lEFERENCJ

NBS TECHNICAL NOTE 714

Reactor Radiation Division:

Annual Progress Report for the

Period Ending October 31, 1971
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards1 was established by an act of Congress March 3,

1 901 . The Bureau's overall goal is .to strengthen and advance the Nation's science and

technology and facilitate their effective "application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measure- ment system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Center for Computer Sciences and

Technology, and the Office for Information Programs.

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Radiation2—Nuclear Radiation2—Applied Radiation2—Quantum Electronics3—

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. THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research lead- ing to improved methods of ' measurement, standards, and data on the properties of

well-characterized materials needed by industry, commerce, educational institutions, and

Government; provides advisory and research services to other Government agencies; and develops, produces, and distributes standard reference materials. The Institute consists of the Office of Standard Reference Materials and the following divisions: Analytical Chemistry—Polymers—Metallurgy—Inorganic Materials—Reactor

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2 Part of the Center for Radiation Research.

3 Located at Boulder, Colorado 80302.
ONAL BUREAU OF STANDARDS

MA

Y\j4 Vnr~ QV UNITED STATES DEPARTMENT OF COMMERCE

Peter G. Peterson, Secretary

V/S NATIONAL BUREAU OF STANDARDS • Lewis M. Branscomb, Director

in

NBS

-t TECHNICAL NOTE 714

ISSUED MARCH 1972

Nat. Bur. Stand. (U.S.), Tech. Note 714, 108 pages (MAR. 1972)

CODEN: NBTNAE

Reactor Radiation Division:

Annual Progress Report

for the Period Ending October 31, 1971

Robert S. Carter, Editor

Reactor Radiation Division

Institute for Materials Research

National Bureau of Standards

Washington, D.C. 20234

*<"«*>

V*u of "

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be

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FOREWORD

The National Bureau of Standards Reactor was built not only to serve the needs of the

NBS but also those of the greater Washington Scientific Community and other government

agencies. The Reactor Radiation Division was established to operate the reactor and to

foster its scientific and technological use. Toward this end, the Division has a small

nucleus of scientists experienced in the use of reactors for a wide range of scientific and

technical problems. In addition to pursuing their own research and developing sophisticated

experimental facilities, they actively seek out and encourage collaboration with other

scientists, engaged in challenging programs, whose work can benefit from use of the reactor,

but who as yet do not have the reactor experience necessary to take full advantage of the

facilities available. The Division also provides irradiation services to a wide variety

of users as well as engineering and other technical services.

The reactor operates at 10 Mw and is designed to provide a broad spectrum of facilities

ranging from intense neutron beams to extensive irradiation facilities, making it one of the

most versatile high flux Research Reactors in the country. Thus it is able to serve a large

number of scientists and engineers in a broad range of activities both within and outside

the NBS.

Use of the reactor by individuals and organizations outside the Reactor Radiation

Division has continued at a high level during the past year. Thirty-three scientists from

other parts of the Bureau, representing 20 man-years of effort, use the reactor regularly

either directly or in cooperation with scientists in the Division. An additional 80

scientists, engineers, and technicians from other agencies, universities and industry spent

34 man-years of effort using the reactor during the past year.

The purpose of this report is to summarize the activities of the large number of users

outside the Division as well as the work in the Division. The summaries are divided into

two groups. One is the research activities and the other is the operation and service

activities. The research activities are further broken down into three groups: the first

includes all the work of the Division and most of the collaborative work; the second

describes the activities of our formal interagency collaboration based on long-term arrangements where scientists from other agencies are actually stationed at the reactor; and the

third catagory is the summary of activities of other NBS divisions which use the reactor

directly rather than through collaboration with Reactor Radiation Division scientists.

R. S. Carter, Chief Reactor Radiation Division
REACTOR RADIATION DIVISION

Annual Progress Report

for the period ending October 31, 1971

Edited by R. S. Carter

This report is the annual progress report of the Reactor Radiation Division for the

period October 1, 1970 to October 1, 1971. It summarizes the activities of the large

number of users outside the Division as well of the work in the Division.

Key Words : Crystal structure; diffraction; isotopes; molecular structure; neutron;

nuclear reactor; radiation
TABLE OF CONTENTS

RESEARCH PROGRAMS

Page

Division and Interdivision Collaborative Programs 1

Thermal Neutron Flux Measurements 1 Intercomparison of Neutron Diffractometers 1

Group Theoretical Analysis of Neutron Scattering in Crystals 2

Asymptotic Scattering Theorems 2

Properties of Crystal Lattices: The Derivative Lattices and their Determination ... 3

The Structure of [Co (Imidazole^] (N0„) „ 3 6 3 2

J

The Configuration of the Water Molecule in Cupric Fluoride Dihydrate 9

The Structure of Durene 13

The Structure of Anhydrous Monocalcium Phosphate 14 Neutron Diffraction Study of Two Dental Amalgam Alloys ^4 Refinement of the Structure of Orthoclase 15 Proton Dynamics and Phase Transitions in Transition Metal Hydrides 20

1. Vanadium Hydrides 20

2. Tantalum Hydrides 23

3. Palladium Hydrides 23 Rotational Dynamics and Order-Disorder Transitions in Ionic and Molecular Crystals . .24

1. Hydrosulfide Salts 24

2 . Potassium Cyanide 28

3. Plastic Crystals 29 Lattice Dynamics Studies 30

1. The Dynamics of Sodium and Potassium Biflouride: Infrared, Raman and Neutron

Studies * 30

2. Dynamics of Potassium Cyanide . . ^ 31

The "Rotator" Phase Transition in n-Alkanes 34

Inelastic Neutron Scattering from Vanadium Above and Below the Superconducting

Transition 34

Neutron Diffraction Studies of Clustering in Cu Ni Alloys 35

Inelastic Neutron Scattering Study of Liquid Neon 36

Liquid Helium Structure Factor at Several Densities Above and Below the X Transition .37

High Resolution Fermi Chopper for Neutron Time-of-Flight Analysis 38

V
Page

Cold-Neutron Time-of-Flight Facility 38

Cold-Neutron Source 39

Publications 41

B. Interagency Collaborative Programs 43

Spin Structure of Erbium in High Magnetic Fields

46 Rare Earth Lead Salt Magnetic Semiconductors

Rare Earth - Cobalt Intermetallic Compounds 46

Structural Studies of Amorphous Solids by Neutron Diffraction 47

The Lattice Dynamics of NaNC>3 48

The Structure of Ammonium Nitrate (IV) 49

Precision Measurement of the Thermal Neutron Scattering Amplitude for Silicon . . . 50

Equipment Development; NBS-NOL-NRL Joint Program 53

1. Triple-Axis Neutron Spectrometer 53

2

Superconducting Magnet 53

3High Temperature Furnace 53

Equipment Development; NBS-Picatinny Arsenal Joint Program 54

Publications • 56

C. Non-Division NBS Programs 57

Measurement of Average Fission Cross Section Ratios 57

Quality Assurance Irradiations for Fast Reactor Materials Dosimetry 57

Activation Analysis Section: Summary of Activities FY 1971 59

1. Biological Standard Reference Materials 59

2. Mercury Analysis 59

3. Californium-252 Neutron Source 60

4. The Nuclear Track Technique 60

5. Mass Separator . 60

Atomic Constants from x-ray and Positronium Decay y-ray Measurements 61

Cobalt-60 Nuclear Thermometry 61

Decay Scheme Studies 62

Parity Violation in Strong Interactions 63

Two-Phonon Emission in (n,p) Capture 63

Fast Neutron 3 He Spectrometer 64

Publications 65

Vi
REACTOR OPERATIONS AND SERVICE PROGRAMS

A. NBSR Operating Summary 67

B. Service Programs 69

Flourine-18 Radiopharmaceutical for Bone Lesion Localization 70

Flourine- 18 Production in the NBS Reactor 75

Studies of the Effects of Parenteral Copper Chelates on Bone Healing 77

Activation Analysis Program of the Food and Drug Administration at the NBSR ... 78

1. Determination of Mercury in Common Foods and Total Diets 78

2. Mercury Distribution in the Central Nervous System of Beagles 78

3. Determination of Bromine in Pigs 78

4. Drug Analysis and Radioisotope Tracer Production 78

5. Analysis for Mercury in Fish, Flour, and Standard Reference Orchard

Leaves by Electrodeposition Radiochemistry . . 79

Scandium Distribution in a Terrestrial Rock 79

Distribution of Elements in Meteoritic Minerals 80

Trace Elements in the Environment 81

The Use of Neutron Activation Analysis in Scientific Crime Detection 83

Federal Bureau of Investigation Activation Analysis Program 84

U. S. Postal Service Activation Analysis Program 85

Development of Analytical Methods and Determination of Constituents of Geological Samples G6

1. Analysis for Gold in Rock Samples 86

2. Gold as a Tracer in Thermal Waters 86

3. Trace Metals in Galena, Sphalerite, Pyrrhotite and Pyrite 86

4. Analysis for La, Sc, Cr, Th, and Au 87

5. Determination of Platinum and Palladium in Geological Materials 87

6. Determination of Tantalum, Antimony and Hafnium in Lunar Samples .... 87

7. Background Levels of Arsenic in Rocks and Soils 87

Study of Radiation Effects on the Transmission Characteristics of Sapphire and

Quartz Windows CG

Feasability Investigations of a Fuel Bundle Motion Monitor 92 vii
Investigation into Neutron Damage of PbS Films 93 Neutron Irradiation of InSb 94 Neutron Activation Analysis of Silicon for MOS Devices 94 Chemical Composition of Particulates Collected in the Marine Atmosphere 95 Studies of Magnetic Properties in Raro Earth Alloys at Cryogenic Temperatures" "95

STAFF ROSTER

A. Division Organization Chart 97

B. Non-RRD NBS Staff located at Reactor 98

C. Guest Workers and Collaborators , 98
RESEARCH PROGRAMS

A. Division and Interdivision Collaborative Programs

Thermal Neutron Flux Measurements

V. W. Myers and M. Ganoczy

A bath consisting of manganese sulfate dissolved in water is being used at one of the

NBSR beamports. The purpose of the experiment is to have a known thermal flux in which

cobalt glass beads can be activated. A neutron beam of the order of a millimeter radius is 56 directed into the bath, and the system is calibrated by the addition of a known Mn

activity into the bath. Cobalt glass beads activated in the known thermal flux can then be

used for calibrating a counting apparatus. An unknown thermal flux can then be measured by

activating an identical cobalt glass bead in the flux and then counting it in the calibrated

counting system.

Intercomparison of Neutron Diffractometers

V. W. Myers

The Reactor Division is collaborating in a program sponsored by the International

Union of Crystallography for comparison of neutron flux at various neutron diffraction

instruments around the world. Gold foils are activated at the spectrometers and then

sent to one of the following laboratories for counting: Australian Atomic Energy

Commission: Institutt for Atomenergi, Kjeller, Norway; NBS . The NBS counting apparatus

was calibrated by activating a gold foil in the thermal neutron density standard maintained

at the Center for Radiation Research. The Kjeller and NBS counting facilities have been

intercompared by means of a gold foil that was irradiated at Kjeller and counted at both

of these facilities. The Kjeller and NBS results on the gold foil's d.p.s. differ only

about 1 percent. This is satisfactory since the two counting facilities were calibrated

independently of one another, and the inherent accuracy of each facility is of the order

of 2 percent.
Group Theoretical Analysis of Neutron Scattering in Crystals

R. C. Casella

and

S . F . Trevino

(Picatinny Arsenal)

A general program for employing projection operator techniques (first suggested by

Elliott and Thorpe ) to study the effects of crystal symmetry on the structure function

for inelastic neutron scattering is being implemented. Certain logical difficulties in the

original proposal have been overcome and simplifications introduced. The method has been

applied to NaNO (See K. W. Logan, S. F. Trevino, R. C. Casella, et al . , Interagency

Collaborative Programs, Sec. B) and a paper submitted for publication. Further work on

Brillouin-zone-boundary and other general related problems is in progress and expected

to continue

Asymptotic Scattering Theorems

R. C. Casella

Work on the form of the elastic cross section do/dt, (t= momentum transfer) when total

cross sections satisfy a (AB) ^ a(AB) as the square of the cm. energy s •* «. has continued,

based upon Casella 's earlier discovery of an infinite number of zeros in the analytic

2 continuation of the scattering amplitude in the variable x= (Ins) (-t) . [ A=anti-A]

The degree to which the zeros approach the physical axis in this variable determines the

amount of dampening of possible oscillations in do/dt caused by the zeros. A paper was

submitted for publication in the "Ettore Majorana" series, edited by A. Zichichi. Work

has begun in an attempt to understand the nature of inclusive reactions, A + B •* C +

anything, and the origin of the emperical result, max J (resonance) ocs , in view of the

unitarity relation, max J(total) <*/s Ins. [J= angular momentum].
Properties of Crystal Lattices: The Derivative Lattices and Their Determination

A. Santoro

and

A. D. Mighell

(Inorganic Materials Division)

A method has been developed for driving the superlattices and sublattices from a

general lattice, and a Table of Matrices S for generating all unique superlattices

associated with a lattice for S = 2,3,4 has been derived. The matrices for generating the

unique sublattices can be obtained by taking the transpose of the inverse of the matrices

S.

The Structure of [Co ( Imidazole) A (NO J

„

6 3 2 A. D. Mighell and C. W. Reimann

(Inorganic Materials Division)

and

A. Santoro and E. Prince

As part of a continuing study of compounds containing metal-organic complex cations,

the structure of [Co ( Imidazole) , ] (NO ) „ has been determined by x-ray and neutron diffraction.

6 3 2 This study was carried out in order to obtain accurate parameters of the imidazole molecule

and to work out the details of hydrogen bonding in the packing of the cations. In addition,

a comparison of the results of the x-ray and neutron diffraction determination is of interest

in itself, as only a few compounds of this complexity have been studied with both techniques.

Finally neutron diffraction is particularly suited for this complex, as the crystal shows

no damage when exposed to neutrons

.

In Table 1 the bond distances and angles for the imidazole ring found in the recent

study are reported for the x-ray determination (column 4) and for the neutron determination

(column 5). Corresponding quantities agree quite closely. In the table, the bond distances

and angles obtained in the present study are compared with those found in molecular

imidazole (column 2), in Im,_Ni (NOJ „ (column 3), Im,.Cd(NOj., (column 6) and ImCd(OH)

6 3 2 6 3 2 6 (NO ) "4H (column 7) . The data in Table 1 shows that although the interaction between the

rings and their environment is not the same in all the compounds compared, the geometry of

the imidazole ring is remarkably constant.

3
The positions of the hydrogen atoms were determined by neutron diffraction and the

bond distances involving these atoms are given in Fig. 1. This unambiguous location of the

hydrogen atoms completely clarifies the hydrogen bonding in the crystal. Fig. 2 shows a

projection of the structure of Im Co (NO ) . Note that the distances between the nitrogen

atom N(2) and the oxygen atoms 0(1) , 0(2) , and 0(3') are all consistent with hydrogen bonding

between the hydrogen atom H(4) (attached to N(2)) and these oxygen atoms. However, the

neutron study shows conclusively that the distance H(4) ...0(2) is 2.44A and the distance

H(4)...0(3') is 2. 79A and the distance H (4) .. .0(1) isl.99A. As two of these H .. .0

o distances are greater than the 2.4A limit for hydrogen bonding to oxygen (Hamilton and

Ibers , Hydrogen Bonding in Solids, Benjamin Inc., New York, 1968) , only the H(4) ...0(1)

interaction is a hydrogen bond.

++ The complex cation Im Co determined with x -ray and neutron diffraction methods is

6 illustrated in Figs. 3 and 4, respectively. A comparison between the two figures shows

that the shapes and the orientation of the thermal motion ellipsoids are very similar

for the two determinations . In the imidazole rings the directions of the largest vibration

tend to be perpendicular to the planes of the rings. This is particularly evident if one

observes the thermal ellipsoids of the hydrogen atoms in Fig. 4.
CD

r-* U

as o

N in

•H I

o< o '3'nnr-ir-ior-i-lffiooioco^'

*o .-i m ^o m r- •* rorocornmmLnr-HvQP-tyir--^ • Oi-HOOOCMCMO C\|Hi-li-li-IH„r-)HHHHHHcn

ro^iniDiDLnrooiro^'d'CNCN

i-(VOir>r~»OvOi-Hiflr~«vO<yicr>0

ID .-H CM in "31 ID nromcnroroi£>or^'£>cDon OrHOOOro(N CNiHHHr-li-lr-IHi-li-li-IHH

tn CO CO 00

ro ld in *x>

co cm co in

~ U a U U

Z I l I I + i-H H CM (N + — '-' — -' s z u a u

n en co

o

1 u

1 3

1 CN CN + Z U

+S

H rH a

i o1 a

i +

+

^^ + s H +

^^ s r—

i

a

i

i H

+ H O

+ O

s a —

S3

rcj

TjC

rd

>1 rcl in

s^ 4-J CM c u H

CQ H

Ifl Tl M «. 4-1 4-i U • u .* Ti U) P

< V) c >i 3 01 U >1 3 -U U in M

^-^ H c; ID w C rtJ £

\o r4 4-1 4-1 <rt cn 5

4-> H in < *. C) ^ a c < »a H •H

(1 4J <J\ 4-1 o

-H Cfl ID O 14

«• 4-1 H cy> CO m O > iH M 4-1 m CO (1)

'—

'

IH a

(U i4 Tl 144 of u M-l r-{ •H CO u 14-1 Tl as Tl

as H M Tl U n3 eel <n 4-> G G

1 Tl m <1J at N >i c (M i4 <U ra m 4-1 4-1 rH C M 4-1 0) U H •r4 I U) O <1) 0) -M X ro 4-1 c A

u <D ^ C CT> rd >< .c rcl as >1 •H y CO H Uh 01 ca S
Co

[2.1728]

(2.1599)

r, X^

[124.14]

(124.27)

H(3)_

C(3)

[127.87] X [109.68]

(131.11) \ (109.32)

[1.368] V. 11.324]

<(1 - 378)

[105.39]NJ-313>

(105.21)

[125.49]

(124.87)

[111.50]

(111.27)

C(l)

H(D

[123.00]

(123.81)

[1.358]

(1.354)

11.339]

(1.334)

[105.92]

(106.43)

[132.43] C (2). (127.57)

' A

/

H(2)

[121.63]

(125.97)

[1.358]

(1.357)

[107.48]

(107.75)

N(2)

[125.05]

(126.63)

H(4)

Fig. 1. Bond distances and angles for the coordinated imidazole ring in hexakis (imidazole)

cobalt(II) nitrate. The angles and distances in brackets were determined by

neutron diffraction and those in parenthesis by x-ray diffraction.
•H
Fig. 3,

Fig. 4. 8
The Configuration of the Water Molecule in Cupric Fluoride Dihydrate

E. Prince

Cupric fluoride dihydrate, CuF -2H 0, was one of the first hydrated crystals to have its

structure determined by single-crystal, neutron-diffraction techniques. In the original

determination the H-O-H bond angle in the water molecule was found to be 115.5+,4°, in

contrast to a value of 104.5 in a free water molecule in the vapor phase. As a much larger

number of structure determinations became available, it appeared that this value of the

bond angle was considerably out of line with those found in other, similar crystals. The

original determination was done with 3 sets of 2-dimensional data taken on 3 different

crystals mounted with 3 different axes vertical. Only 6 OkO reflections were common to

the 3 sets, and several of these were known to be affected strongly by secondary extinction.

In view of the uncertainties in the original determination and the fact that the structure

appeared to be unusual, a redetermination of the structure was undertaken, using 3-dimensional

data taken from 1 crystal.

CuF -2H is monoclinic, with cell dimensions a=6.7060A, b=7.3958A, c=3.3002A,

0=109.38° Z=2, space group C2/m. Of 168 reflections within the limits of the diff ractometer

there was observable intensity for 163. A least-squares refinement of these data led to a

final weighted R index of .038 and the parameters shown in Table 1. Fig. 1 shows the

8-membered ring formed by 2 water molecules and the fluorine atoms to which they are

hydrogen bonded, together with the copper atoms that coordinate to the water molecules.

The H-O-H bond angles is 110. 6+. 2°, which is much more in line with the values found in

similar, hydrated crystals. Note, however, that this angle is still larger than the F-O-F

angle (96. 5° 1 ) , which indicates that the presence of the hydrogen bond is not the principal

cause of the opening of the bond angle from the free molecule value. The observed value is

close to the tetrahedral angle of 109.5° which may be the preferred angle for a water molecule

bond in this type of structure.
<0

o

ina8

•p

n)

•rH

o -^

<HM

H

0) V

0)1

M D

IB tn ft •Hm

O

•H 4J B c

IT) JJ U

<d •rl

M-l iH ^

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CO

CO

en

COen

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T3O

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fa

11
12
The Structure of Durene

E. Prince, L. W. Schroeder and J. J. Rush

The work on the crystal structure of durene (1 , 2 ,4 ,5-tetramethyl benzene) described in

the 1970 progress report has continued during this year. The structure is monoclinic,

space group P2 /a, with a=11.57A, b=5.77A, c=7.03A, 8=112.03°. Of 870 independent reflections

within range of the diffractometer 485 had intensities significantly above background. The

data have been refined by least squares methods, using several different weighting schemes;

the lowest value of the weighted R index achieved so far is Rw = .066.

At this level the general features of the structure are clear, but certain details are

inconsistent, and the refinement cannot be considered completely satisfactory. The position

parameters for the carbon atoms indicate a molecular structure (see Fig. 1) which is

exactly planar within the precision of measurement, with C-C distances, both within the

ring and between the ring and the methyl groups , very close to the expected values for

this type of compound. There is, however, excessive scatter in the C-H distances. Also,

although all of the thermal ellipsoids correspond qualitatively to what would be expected

from a model which makes the principal thermal motion a libration of the entire molecule

about its axis of maximum inertia, to which are added librations of the methyl groups

around the C-C bond, there are some glaring inconsistencies. In particular, the hydrogen

atom attached to the ring, H4, should not have a component of its greatest vibrational

amplitude parallel to the C-H bond, and the tangential component of the motion of

hydrogen H3 is less than the similar component of the carbon on which it is riding,

which is obviously impossible.

A study of the refinement methods that can be applied to this data set is continuing,

and an additional data set will be collected at low temperature.

13
The Structure of Anhydrous Monocalcium Phosphate

B. Dickens

(Polymers Division)

and

E. Prince

The Dental Research Section of the Polymers Division of NBS is conducting crystallographic studies of calcium phosphates and carbonates and related compounds. The

knowledge gained is expected to provide insight into processes of mineralization in vivo .

The complete characterization of many of ihese compounds includes knowlecge of the positions

and thermal parameters of hydrogen atoms. 1212 reflections have been measured by neutron

diffraction on a single crystal of Ca(H PO ) and the hydrogen positions have been found.

Two of the five crystallographically different hydrogens in the crystal structure are

nominally centered between their coordinated oxygen atoms. Such hydrogen bonds are

chemically important and are of considerable theoretical interest. In the case of

Ca(H PO ) , however, abnormally great secondary extinction effects have mitigated further

analysis because the limits of the usual correction formulas have been exceeded and the therma.

parameters probably contain appreciable systematic error. More accurate ways of applying

the extinction correction are being studied.

Neutron Diffraction Study of Two Dental Amalgam Alloys

R. M. Waterstrat

(Polymers Division)

Dental amalgams are silver-tin-mercury alloys which are widely used in restorative

dentistry. The amalgam is prepared by mixing a silver-tin alloy powder (Ag

3 Sn) with

liquid mercury to form a metallic paste which can be shaped to conform to the tooth

cavity. After the alloy hardens by a diffusion reaction, it is essentially a composite

material consisting of partially reacted Ag

3 Sn particles (y phase) which are bound

together in a matrix of finely crystalline Ag^ compounds (Y

1 phase) and Sn

?Hg compound

(Y phase)

Recent work by Dr. L. B. Johnson at the University of Virginia has demonstrated that

the formation of the tin-mercury compound (y phase) can be prevented or at least suppressed

14
by the addition of about 10% gold to the silver-tin alloy powder (y phase) . This produces a

dental amalgam which is probably more resistant to degradation since the y phase is the

softest and most easily corroded of the three constituent phases. Dr. Johnson's findings,

however, were based largely on x-ray diffraction data. X-rays reveal information mainly

from a thin surface layer rather than from the entire volume of the sample. Furthermore,

the x-ray data is subject to much uncertainty since crystals within the thin surface layer

may be strongly oriented. A relatively small preferred orientation of the crystals would

produce significant changes in the x-ray intensities and would make it very difficult to

estimate the relative percentages of each phase in the alloy.

R. M. Waterstrat of the NBS Dental Research Section suggested to Dr. Johnson that

neutron diffraction would be a more suitable experimental method than x-ray diffraction

* since the neutron beam is capable of penetrating a much larger volume of the sample .

Dr. Johnson subsequently furnished samples of his new dental amalgam prepared from the 10%

Au alloy and also from a conventional alloy without the Au addition. These samples were

examined by neutron diffraction at the NBS reactor in cooperation with Dr. S. Pickart,

Dr. J. J. Rhyne and Dr. E. Prince of the reactor group.

A comparison of neutron diffraction patterns from the two amalgam samples has

revealed that lines due to the y phase, which were present in the pattern from the

conventional amalgam, were entirely absent in the pattern from Dr. Johnson's 10% Au amalgam.

One may, therefore, conclude that the Au addition has either eliminated or greatly

suppressed the formation of the y phase. In addition there was some evidence for a new

Au-containing phase in Dr. Johnson's alloy since an unidentified line appeared in the

pattern from this amalgam which did not appear in the pattern from the conventional amalgam.

A comparison of the relative line intensities also suggested that Dr. Johnson's alloy

contained a greater percentage of unreacted phase particles than the conventional alloy.

These findings are all compatible with Dr. Johnson's suggestion that the new amalgam will

prove to be more durable than the amalgams now being used in dentistry.

The mass absorption coefficients for Ag and Hg irradiated by X-rays (CuKa ) are 223 and 223

while for neutron irradiation the corresponding values are 0.20 and 0.63, respectively.

These values may be used to calculate that about 99% of incident x-rays are absorbed by a

IS
0.02 ram surface layer of the amalgam whereas only about 1% of incident neutrons would be

absorbed in a 5 mm layer. The cylindrical samples which were used in the neutron diffraction

study were irradiated in a direction perpendicular to the cylinder axis and were about 6 mm

in diameter.

Refinement of the Structure of Orthoclase

E. Prince

and

G . Donnay

(Dept. of Geological Sciences, McGill University

Montreal, PQ, Canada)

Orthoclase is a feldspar , a class of alumino-silicate minerals which is one of the

major constituents of the rocks in the earth's crust. The basic structure is one of MO.

4 tetrahedra linked together by sharing the oxygen atoms at the corners between neighboring

tetrahedra. The distribution of aluminum among crystallographically nonequivalent

tetrahedral sites is of great interest to geologists, because the degree of order or

disorder can be correlated with the thermal history of the rocks in which the mineral is

found. Also, there have recently been suggestions that a substantial amount of water could

be bound in the supposedly anhydrous minerals of the earth's crust by means of small

amounts of substitution of OH ions for O ions in these crystals.

Aluminum and silicon are neighbors in the periodic table, so they cannot be distinguished

by x-ray diffraction on the bases of scattering amplitude alone. Unfortunately the scattering amplitudes for neutrons for these elements are also very similar. Because of this, all

attempts to determine the Si-Al distribution have made use of the fact that the Al3+ ion

4+

is significantly larger than the Si ion, and therefore the ionic occupancies are directly

related to the M-0 distances, as determined from an accurate refinement of the crystal

structure. The M-0 distance in this type of structure varies approximately linearly with

aluminum content from 1.61A for pure SiO to 1.75A for pure A10 . A neutron diffraction

refinement of the orthoclase structure was undertaken in order to determine the distances

accurately, and to see if there was any indication of the presence of OH in the

structure.

.16
There is evidence that the true structure is triclinic, with cell dimensions a=8.5610&,

b=12.965A, c=7.2-77A, a=90.048°, 3=116.059°, y=89.814°. However, a systematic comparison

of reflections of the type hkJi. with reflections hkJi did not reveal any significant

department from monoclinic symmetry. Therefore, in the refinement, the a and y angles were

assumed to be 90°, and the refinement refers to an "averaged" clinic structure. Of 764

reflections within the range of the diff ractometer , 721 had observable intensities. A

least squares refinement using these data "gave a final weighted R index

2 2 1/2

(R =[£ (F -F ) /I F ] ) of .038 with the atomic parameters listed in Table 1. w w o c w o Figure 1 shows the configurations of the two MO tetrahedra. The mean MO distances

indicate that site SI1 contains approximately 1/3 aluminum and 2/3 silicon.

17
9>

HI

rrj Ho5u

M-l

<uU • a (I) 4J U

t) 3

tn c rl

+J IH

in +)

0) c £ <ri 3j rl

IH M-l rlC p m c H

01 V)

0) 4J

x:

+J U-l ho in u c

IH (i •rl VI 4-1

l-l «f

(11 •rl

4-1 >

(I) (1) s T3

!-* T) m rl u< ia Tl u C

rH

m

fi 4-> n 01 p

rt (11 .c

<-i 4J

<ac (V

•rl V) Um tfl

r~ t * in ^r * ro

n

(N

r~ in

i-H on o ro

H

H

(N ^ in in <£> in in a1 * * ro

-I <N

Oo

<N

CO rH

co ro

en

M rH rH ^ <-K (N t-t

in in ID in in •& * 1 r-J 00 M1 o

ro

(N

ro

ro

in

in in i£ kD in * T

D VD CN

a-o

VD

00

O ro

CO

rH (N c < < m u Q 3 o O o o o * M

18
Pig. 1. Stereo pairs showing the configurations of the two M-0 tetrahedra in orthoclase.

The standard durations of M-0 bond lengths are .002A.

19
Proton Dynamics and Phase Transitions in Transition Metal Hydrides

Work has continued on a systematic study of the diffusion and vibrational dynamics of

hydrogen bond in polymorphic transition-metal hydrides. The work completed or in progress

on several hydride systems is summarized below:

1. Vanadium Hydrides- L. A. de Graaf and J. J. Rush

In collaboration with H. E. Flotow and J. M. Rowe of Argonne National Laboratory, we

have analyzed in detail inelastic scattering spectra measured previously for the a (bcc)

phase of VH and the a and 6 (bet) phases of VH over a range of neutron momentum

°-l transfer (Q) of 2.0-4.1A . Some of the measured spectra are shown in Fig. 1, with the

separation into inelastic scattering (horizontal line) , elastic scattering from vanadium and

quasielastic scattering from the protons indicated. The extension of our measurements of

quasielastic line broadening to larger momentum transfers than those available with cold

(4A) neutrons by the use of an incident wavelength of 2.42A has proved to be essential in

obtaining definite information about the jump mechanism of the hydrogens in the bcc lattice.

The measured full widths at half maximum of the quasielastic peaks for VH at 212°C have

been compared with widths calculated for several models involving jumps between octahedral

and tetrahedral interstitial sites. The experimental and theoretical results are shown

in Fig. 2, along with the previous cold neutron data. None of the models tested predict

the rapid increase of the line width at large Q, but from the behavior of the width curves

2 °-2 for VH at Q <14A we conclude that the diffusion in a-VH is dominated by jumps

between first-neighbor tetrahedral sites. This is the first time to our knowledge that

jump mechanisms have been established for a Group V-A metal-hydride.

A number of possible deficiencies of the jump diffusion model have been examined and

we have tentatively concluded that the most important factor is the assumption of instantaneous jumps. Due to the very rapid diffusion in a VH the relaxation (residence) times derived

from our results are about 0.5 and 1 ps (1 ps = 10 sec) for VH and VH , 1/2 respectively, whereas the jump time between sites is M1.04 M

' ,. ps (M „ is the effective

eff eff mass of the "dressed" proton in the lattice) . Thus the jump time is not "instantaneous" but

is approaching comparability with the residence time between jumps. This apparently explains

the more rapid breakdown of the jump diffusion model for VH (Fig. 2) and the differences

in the measured quasi Debye Waller factors both between VH and VH and between those

derived from the present measurements and the earlier cold neutron data. We are currently

20
8-

_ 2-

oo

13 ^ m" 3 or -& <

co >

H

00

-z. UJH

2-

1 1

- VHo.|98

i. i

<j>=48.3° .

" T=485K

-

• m -

1 »

. ... ..I...'"*' 1 1 • • r i 1 4

- VHo.198 -

<t»=85.5° . - T=485K * \

- • •

i

i

1 "••—'

-15 -!0

2h

8

5 10 -15 -10 -5

FREQUENCY TRANSFER (ps'

1 )

r —

' 1

1

VHq.57

•v

<|>=48.5 *"

. T=485K ".*

." .* • ./

/ •

*

'.

% " t

...

'

**•••**• i

| i

i i

" VHq.57

1 1

$=85.8

. T=485K

.v

-

>* V

• «* » • / V

"•!• '"

1 —i 1 '

10

Fig. 1. The separation of the measured spectra I(<l>,w) in inelastic, elastic, and quasielastic components. The data points are given by triangles, the points

corrected for vanadium scattering by dots.

21
(,.sd) 2^v

(,.sd)

2/Uv

10c * *. rl (11 cd CO 10 P 4J x: CD CD

V

CJ rH jJ -P •P CO

•--1 3 u •rH r|

a -0 in >P CO CO <v 0) £

en

u ^ r-H •~l in a (0 CT> id id cu •P •rH u rl o

<u -C iH CD "9 -a II 5

•P 3 c CD CD P

to 1 s x -P

(1) CD

p id

H

.c (H ^ CO 4J

•P id <u 3 *• •H CU u CD (0 3 CO

ri 5

id

CD rl P CD •P T) <d c rl H

0)

A CD £

CO

H rl c

(0

u id CD o> s rH

a. CD •H &l id E u co 3 CD H rl u CD P G CD T3 u <a 1-1 CD 1 C CD o XI 4J X!

<N

x

u io -P id s, •p •H 10 CD co u

J

H •.h

U

a

U CD -p 3 3 id rl <D < a CD id •P

in CD

n c CD * <u rH c -a

CO rH rH c 1 a

>!u r| CD

p id

id Ih M-l

H CD

X

0) •H 3 CD rH a CD CD •P C id £ > CD rl o a p rl XI a 0

•rl <D 3 c CD P a *. U 10 id X

co (0 id n) +J E p 4J

r-H cu c n 3 CO

<D £ CD • •r-i CD H H §

CO rl

(0 +J id c

IT)

u c CM CD CD 3 3 CD c CD • tr ,—

CO E » 3 CO P id •rH CO c •P a

0)

X CD rl

a CD CD xi CD £ CD CD XI •-< p P a o 3 o -p !< • -P CO • KH 0) c CD rH CD a o

0) CD II XI 1 CO CO C 3 P

in CD

O

H co -n

x:U

M * a (H P (0 a P 10 -a rH 3 CD 3 •• •H <u CD CD 4J n •a1 CO 3 T3 X C r| a

-P 1 CO T) E Tl ro CO rH

(VC

H rH

a rH

rl r-H rl id - 3 <u O rl CO o o

CO rl T3 TS

a •

II

a a> CDu CD CN

ai > c w

•s

en II e (U rl •rl OJ CN

H

(A >d r-l rl r- II CD P M P H II x: <H xi id CD II rH

p

Eh CD P |H

H t22
preparing a paper for publication which fully discusses these results and their implications.

2. Tantalum Hydrides - L. A. de Graaf , R. L. Livingston, and J. J. Rush

In collaboration with H. E. Flotow of Argonne National Laboratory we have extended our

neutron scattering studies of the Group V-A metals to tantalum hydride. Spectra have been

measured for a-TaH„ , , at temperatures from 22 to 340°C and momentum transfers of 0.45 to 0.1b

° —

3.6A . These data are presently being analyzed. Preliminary examination of the quasielastic line widths seems to indicate a leveling off at high Q. In addition our preliminary

results indicate a considerably higher activation energy for diffusion and lower diffusion

rate for the hydride. Such results would be consistent with the ideas and theoretical

predictions developed in the explanation of the VH results described above. Work is

continuing on the analysis of the TaH . _ data, including a comparison with various diffusion

models and calculation of quasifrequency distributions for the hydrogen vibrations. Further

experiments with other hydrogen concentrations are planned.

3. Palladium Hydrides - L. A. de Graaf and J. J. Rush

In collaboration with G. A. Ferguson of the Naval Research Laboratory, a large single

crystal of palladium (f.c.c. structure) has been electrolytically loaded to a concentration

of PdH . This crystal will be used for a detailed study of the diffusion of hydrogen in

various crystal directions by quasielastic neutron scattering using the new four-rotor

cold-neutron beam facility at the NBSR.

A smaller Pd single crystal has been loaded with deuterium to PdD to text the

quality (mosaic spread) of the resulting "crystal" for future lattice dynamics experiments.

A neutron diffraction examination showed an effective mosaic spread about 2-3 times greater

than is desired. Further tests will be tried with different loading conditions.

23
Rotational Dyanmics and Order-Disorder Transitions in Ionic and Molecular Crystals

Work has continued on detailed studies of phase transitions involving orientational

disorder of ionic groups or molecules in crystals. The precise nature of the rotational

disorder in the high temperature (generally cubic) phases of hundreds of inorganic and

organic crystals is not in general well understood - nor is the microscopic basis of the

dramatic changes in physical and thermodynamic properties associated with such phase

transitions. We have chosen several prototype materials (ionic and organic) and are

attempting to obtain a more detailed understanding of the dynamical and structural nature of

such phase transitions by combining results from a variety of techniques including neutron

diffraction and inelastic scattering, infrared spectroscopy and Raman scattering.

1. Hydrosulfide Salts - L. A. de Graaf , J. J. Rush, R. C. Livingston and L. W. Schroeder

The structure, ionic reorientation and vibrational dynamics of sodium hydrosulfide in

both its low-temperature trigonal phase and its high temperature fee "rotator" phase have

been studied by neutron diffraction and inelastic scattering neutron powder pattern

techniques for the trigonal and cubic phases at 296 and 379K, respectively. The results

are shown in Fig. 1. Several possible models describing the orientations of the SH ion

in the trigonal phase were compared with the experimental structure factors. A model in

which the SH ions are aligned along the trigonal axis clearly gave the best agreement

between calculated and observed structure factors. This structure is illustrated in Fig. 2

along with the high temperature fee structure. Thus the transition from the cubic to the

trigonal phase apparently involves alignment of the SH ions along one of the cubic

I diagonals which then becomes shorter than the others, resulting in the less symmetric

trigonal structure. The analysis of the room temperature diffraction data also yielded an

o S-H distance corrected for thermal motion of 1.35A.

Several structural models were also considered for comparison with the cubic phase

results. The isotropic "free rotor" model can be rejected in favor of a less randomly

disordered model by comparison with the neutron inelastic scattering results, which clearly

rule out quasifree or random rotation. The limited diffraction data in this phase,

however, do not enable a distinction to be made between disordered models.

In a related experiment the dynamics of the SH ions in NaSH have been studied by

neutron inelastic scattering using the hybrid time of flight spectrometer at the NBSR. The

incident neutron wavelength was 2.42A and for elastic scattering the time of flight

24
1 i i i i I {200}

1 1 I 1

65 - CUBIC NaSH 379 K

60 {III}

h

1

{2 20}

- "^

°°o/s

o 1 o 1 8 55 K

oo 8

50 ~ W, <222>

45 -

40 -

*V {420}

V

^35

LJ<

—

{110}

VX,

co 30 o

-*

i±j >

1 $75 - 1 TRIGONAL NoSH 296 K ~

_i *o 10

tt ,T70 _ _

tnZ

3

{100}

c

) 8 65 -

s

{221} - z O o

£ 60 — ©°o

1

1o

1

i 3 °o e 1' o 1 111 "Jo ? Z

55 {110} I -

50 —

45

O oIN*

{022}

^V'?. &

1 V\ , ,{322}

40 a»

o.{30iU

35

1 1

i i i 1 1 1

1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 K (K=4irSIN9/X)

Fig. 1. Neutron diffraction patterns of powdered NaSH in cubic and trigonal phases.

25
• No

O S

• 1/2 H

Pig. 2. Composite drawing of the NaSH crystal phases. The SH ions are shown aligned

along [111] of the cubic phase. The three vectors from the Na atom at the corner to Na atoms in a (111) plane define the translations of the trigonal cell.

26
ENERGY TRANSFER (meV)

100 50 30 10 -5

•o

.6

.4

.2

1.0

(/) 1- .8

z

=> .6

>-

a: .4

<

a:i- .2

m

q: 0.

*!«» <

> .8

1-

</> .6

z

UJ 4 H

z

.2

1.0

.8

.6

.4

.2

0.0

T

NqSH

T = I03°C * = 65.3°

T T

v.v -

••"*

S.

'.v-•-*,. A*..

NaSH

T=23°C

*=65.3°

8.5

•• • •• • . . !

'•**'1$'!i..A:«&iy! •

1.0 1.5 2.0 2.5 3.0

NEUTRON WAVELENGTH (A)

Fig. 3. Inelastic neutron spectra vs. neutron wavelength for NaSH in its cubic and

trigonal phases. Intensities are corrected for background, neutron chopper

transmission and detector efficiency.

27
o-l resolution was 3.8% and the momentum transfer (Q) range was 0.4 to 3. 2A . Examples of

measured inelastic scattering spectra above and below the phase transition (T /v360K) are

shown in Fig. 3. The spectrum at 296K in the trigonal phase shows a very sharp elastic

o scattering peak at 2.42A, as well as two bands of inelastically scattered neutrons, one

peaked at ^50 meV (400 cm ) energy gain and the second around 10 meV. The two inelastic

bands are assigned, respectively, to the SH librational modes and to translational lattice

modes . The spectrum measured in the fee phase at 379K shows no great change in the peak

of the librational band, but does exhibit considerable broadening of the elastic scattering

line. This behavior can be directly attributed to the onset of rotational jumping of SH

-12 ions in the lattice on a time scale of ^10 s.

The temperature and Q dependence of the observed broadening has been extracted from the

data and is being compared in detail with theoretical widths calculated using various models

in which the SH ions are assumed to reorient with rapid jumps between a limited number of

quasi-equilibrium positions. Relaxation times and the activation energy for the SH

reorientations should also be derived from our analysis.

Experiments are also currently in progress to synthesize CsSH , an interesting analogue

to the sodium salt, so that neutron spectral measurements may be extended to a study of the

phase transition in this system. It should be noted that these materials are extremely

reactive and thus require considerable care in handling and in preparing neutron sample

holders.

2. Potassium Cyanide - J. J. Rush and E. Prince

KCN is one of the broad group of polymorphic compounds M+XY (including the hydrosulfides discussed above) whose crystal phase immediately below the melting point has a

CN~ ions. Previous attempts to determine the nature of the disorder in the cubic phase of

KCN by x-ray diffraction and by neutron powder diffraction have failed to provide much

information about the orientation and dynamical behavior of the cyanide ions. In view of

this we have, in collaboration with D. L. Price and J. M. Rowe of Argonne National Laboratory,

performed neutron diffraction measurements on single crystals of KCN both at room temperature

and at 180K, close to the phase transition at 167. 5°K. Such single crystal measurements can

obviously provide better intensity data on many more reflections than powder patterns and

thus allow a more meaningful test of various models for the cyanide disorder.

28
In our diffraction measurements all reflections in an octant of reciprocal space were

measured, using an incident neutron wavelength of 1.062A. Sets of data at both 180K and

295K were collected with the crystals mounted in an orientable variable-temperature cryostat

Out of a possible 39 measurable reflections, the number actually observed was 24. The

agreement in intensity within sets of equivalent reflections was excellent. The experimental

structure factors were compared to models in which the CN ions were constrained to be

oriented at random among sets of equivalent crystal directions, namely the (111) , (110) and

(110) directions of the fee cell. Each model fit had as variable parameters (a) thermal

parameters allowing isotropic translational motion of the K ions and both isotropic

translation and libration of the CN ions, (b) the CN distance, (c) an extinction correction,

and (d) a scale factor.

The analysis of these results is almost complete. The tentative conclusions reached

thus far on the basis of a careful examination of the diffraction results and preliminary

force model calculations are as follows

:

2 2 2 a. The non equality of reflections with equal values of (h +K +£_ ) but different

values of h, k, and £_ clearly rules out the possibility of freely rotating cyanide ions.

b. The model fits suggest that the (111) equilibrium orientations are less likely

(contrary to previous predictions) . However the [100] and [110] models give equivalent

fits, so that no definite statments about equilibrium orientations are possible.

c. Very large translational mean-square displacements are predicted from all the fits.

These displacements cannot be explained by any reasonable harmonic model for the lattice

dynamics and may have important implications concerning the nature of the fee phase in KCN.

A publication will be prepared shortly on these results and the effects described above

are being investigated further. Lattice dynamics experiments planned on KCN which are

discussed elsewhere provide a natural extension for our structure study.

3. Plastic Crystals - L. A. de Graaf, R. C. Livingston, and J. J. Rush

Neopentane, C(CH ) , is one of a large group of organic molecules close to spherical in

shape which undergo a crystal phase transition below the melting point from a less symmetric

to a highly symmetric cubic structure. These transitions are analagous to those in the

inorganic crystals described above and are generally associated with large entropy changes

and a waxy or plastic character of the material in the high temperature phase.

29
We have extended our earlier neutron scattering studies to an investigation of the

rotational behavior in neopentane by the careful measurement by infrared spectroscopy and

analysis of the line shape of a vibration-rotation band (at 925 cm ) in both solid phases

and in the liquid. We experienced considerable difficulty in making these measurements due

to the high vapor pressure of neopentane in the plastic (fee) phase. A special variable

temperature cell was designed, constructed and modified until the necessary conditions for

the infrared measurements were achieved. In both the liquid and plastic crystal phases

the observed infrared band is considerably broadened indicating a high degree of rotational

mobility. The band shape narrows sharply in the low- temperature crystal phase. Measurements over a range of temperatures in the plastic phase are being continued. The band

shapes are being analyzed by Fourier inversion to derive correlation functions and times

for the rotational motions . When completed our results will be compared to those obtained

by neutron scattering , so that the information derived by the optical and neutron methods

may be correlated, and a better understanding of the intermolecular forces and rotational

processes may be achieved.

Lattice Dynamics Studies

1. The Dynamics of Sodium and Potassium Bifluoride: Infrared, Raman and Neutron

Studies - J. J. Rush and L. W. Schroeder

Analysis of the spectroscopic results described previously has been completed and the

neutron incoherent scattering spectra obtained for NaHF and KHF have been used to

calculate quasifrequency distributions g'too) for the vibrations of the HF ions. The

g' (a)) derived for NaHF using the one-phonon incoherent approximation is shown in Fig. 1

along with the infrared absorption band observed in the far IR. Our extensive Raman,

infrared and neutron measurements combined with previous data, and comparisons made with

recent spectroscopic and theoretical results on NaN (which has the same R3m crystal

structure as NaHF ) have enabled us to provide a fairly detailed assignment of the internal

and lattice modes for NaHF and KHF . These assignments are listed in Table 1. A publication

on these results has been prepared and submitted.

3n
2. Dynamics of Potassium Cyanide - J. J. Rush

As an extension of our structural studies on the structure and phase transition of

KCN we are currently measuring Laser-Raman spectra of a single crystal of KCN in all of its

crystal phases. The information we obtain on the librational and translational lattice

modes will be correlated with our structural study to seek a better understanding of the

nature of the orientational disorder. The lattice modes measured at q=o will also provide

useful information for our study of the lattice dynamics and interionic forces in KCN which

we hope to begin at the NBSR in the near future in collaboration with scientists from

Argonne National Laboratory.

31
I

•H

•PO

m o if) o If) o

<a- <T to to C\J CM (siiNn Ayvyii8yv)(/?)6

32
TABLE 1. Assignments of internal and lattice modes for NaHF and KHF .

NaHF, Present Assignments (cm ) Previous Assignments (cm )

Mode Active Species

V

3 A

2U

(IR) = 1500 1070

V

2 E (IR) u 1210, 1220

d

893

b

V

l A

lg

(R) 630.5 630.5

L E

g

(R) 145 145

T E (IR) , u A

2u

(IR) 228 (250, sh) 180d -

T" A,,, (IB) E (IR) 90 ITA) f

, 142 (LaI - 2u

1577

226

1150

KHF,

E (IR) *1450 uA

2u

(IR) 1233

Eu(IR)

An (IR) 596 B„ (R) 603 2g

B

ig

(R) E (R) 143.5

s g E (R) 104

e g A„ (IR) , 2E (IR) 2u u A

2u

(IR) , Eu(IR)

1033

912b

895.

5

h

1440

1234

1227

595

1

604 1

i,e 136

ioo 1 '6

146, 174, 130

1045

891

v.= internal mode; L = Libration mode; T = Translatory (optical) mode; T' = acoustic mode; LA = longitudinal acoustic modes; TA = transverse acoustic modes; IR = infrared active; and

R = Raman active.

value for DF2 ~ "defect" concentration.

'Estimated from frequency for DF ~ using an isotope shift H/D = 1.40.

1 . From our neutron scattering spectrum.

a"A rigorous assignment of these L and T modes would require polarization single crystal Raman spectra.

33
The "Rotator" Phase Transition in n-Alkanes

John D. Barnes

(Polymers Division)

Since the last reporting period a further series of inelastic scattering measurements

were carried out on n-nonadecane . The instrument used was the crystal-monochromator , Fermi

chopper facility located at the BT-5 beamport.

These experiments differed from the previous one in that considerably more refined

sample preparation and containment procedures were used. Neutron spectra were measured over

o , o-l

a range of momentum transfers (for elastic scattering) from 0.4A_± to 3 . 2A . A large

number of Vanadium runs were made in an attempt to characterize the instrumental resolution

more completely than in the previous experiments. n-Eicosane was selected as being worthy

of attention because it is the next member of the n-alkane series above n-nonadecane and

it does not exhibit a solid-solid phase transition below its melting temperature.

Measurements on n-nonadecane at 77 K were made for the purpose of confirming some of the

structure found in the weighted frequency distributions measured at higher temperatures.

The scattering angles used in these experiments were dictated by a desire to avoid

significant contributions from coherent Bragg scattering.

A model for the diffusive broadening observed in the quasileastic peaks measured on

n-nonadecane in the Solid I ("rotator") phase has been developed. This model is based on

a particle performing a random walk among a series of equally spaced sites on a circle. The

self-correlation function G (r,t) can be calculated in a closed form for this model. The

s Fourier transform of G (r,t) , namely the "Scattering Law", can likewise be calculated in

closed form. The fitting of this model to experimental data is now being done.

Inelastic Neutron Scattering from Vanadium Above and Below the Superconducting Transition

Bernard Mozer

(Inorganic Materials Division)

Inelastic neutron scattering data has been obtained from vanadium at 5.6K, a temperature

above the superconducting transition temperature, 5.21K, and at a temperature of 4.5K. Data

were obtained using 1.5A and 2.45A neutrons at several scattering angles using the Fermi

chopper time-of -flight system installed at the NBS reactor. The 1.5A neutrons, obtained

2 A
from (111) planes of a copper monochromater , were used to study the whole excitation spectra

of vanadium. The resolution over most of the spectra is determined by the spread in energy

in the incoming beam from the crystal mosaic and collimating systems. The energy spread

-3 o is about 2 x 10 e.v. The 2.45A beam was used to study the lower energy part of the

excitation spectra where the energy resolution in the incoming beam is 0.7 x 10 e.v.

Preliminary results indicate that the excitation spectra of vanadium above and below the

superconducting transition are very similar yet there are indications of differences.

Additional work is in progress to elucidate these differences.

62 Neutron Diffraction Studies of Clustering in Cu Ni. Alloys

Bernard Mozer

(Inorganic Materials Division)

62 Cu Ni alloys made with essentially nickel-62 isotope were prepared for neutron

diffraction studies of clustering in these alloys. The alloys were made by Mr. D. Fickle,

of the NBS Metalurgy Division, in an induction furnace in beryllia crucibles and cold rolled

to plates with three vacuum anneals at 1000°C for strain relief and homogenization. The

last anneal was performed after all cold working and the sample allowed to furnace cool.

Alloys of nominally X=0.20, 0.40, 0.525, 0.60 and 0.80 were prepared in the above method.

Part of the alloy Cu Ni

Q was sent to Professor P. Beck of the University of

Illinois to attempt a quench of the specimen from 1000°C. Neutron diffraction studies were

performed on all the specimens. Diffraction data was taken with a 2.47A neutron beam

provided by the (002) reflection of an oriented pyrolytic graphite monochromator . A 2-1/2

inch filter of pyrolytic graphite was used to remove (<0.1%) the X/2 contamination. Twenty

minute collimators were used in-pile , after the monchromator , and before the counter

.

Diffraction data and background data were taken with counting statistics of 0.1%. Evidence

for clustering is readily observed in the raw data in all the alloys , preliminary data

anaylsis indicates little difference in clustering for the furnace cooled sample and the

quenched sample at the identical composition. Data are being analyzed for the short-rangeorder parameters of these alloys.

35
Inelastic Neutron Scattering Study of Liquid Neon

Bernard Mozer

(Inorganic Materials Division)

and

L. A. de Graaf

o The inelastic scattering of 2.44A neutrons from liquid neon at a temperature of 35.05°K

and a pressure of 21.4 atm has been studied on a time-of -flight spectrometer at the NBS

°—

reactor. The momentum transfer range covered in the experiment was 1.2 - 4 . 1A . The

total resolution for elastic scattering as measured at the detector position was 3.7% for

AX/X which includes the resolution of the monochromator and collimation systems and 2.2%

from the burst width of the chopper. The dynamic structure factor S(Q,u) was obtained

from the experimental data after applying corrections for detector efficiency, chopper

transmission, background from the sample cell and cryostat, and multiple scattering effects.

Special attention was given to the calculation of multiple scattering effects and to

subtraction of the background scattering from the sample cell. The zeroth moment of S(Q,u)

has been compared with the static structure factor S(Q) for liquid neon obtained from a

recent neutron diffraction experiment at the same temperature and pressure as in the

present experiments.

The full width at half maximum of S(Q,co) and the dispersion curve u (Q) were obtained

max

and both corrected for the broadening due to the finite resolution of the spectrometer.

5(Q,(o) and 10 (Q) plotted versus Q show a behavior similar to that observed in liquid max x '

argon. A comparison was made between the experimental results and different theories and

models for simple classical liquids.

36
Liquid Helium Structure Factor at Several Densities Above and Below the A Transition

Bernard Mozer

(Inorganic Materials Division)

L. A. de Graaf

and

Bernard LeNeindre, Guest Worker

(Heat Division)

Preliminary neutron diffraction data has been taken on liquid helium at 12.53, 8.06,

4.15 and 3.97 atmospheres and at T = 2.91K. An attempt was also made to obtain neutron

diffraction data below the transition at a temperature of roughly 2K for the same densities

corresponding to the above pressures. The sample cell was thin walled Ti alloy with little

coherent scattering. Although the alloy has almost flat neutron diffraction data it has

poor thermal properties and we were unable to reach the same temperature below the X °-l °-l transition for the several densities. Diffraction data in the X region 1 . 5A to 4.60A

O —I O 1 had some data from 3 . 5A to 7.0A ± were taken. The data show density effects such that

information on the three-body correlation function can be readily deduced from the density

derivative of the structure factor at constant temperature.

A new sample cell has been constructed and tested. The new cell has titanium alloy

walls with a base of good thermal transport properties at low temperatures . A good thermal

path from the bath to the cell via this base is incorporated in a thermal radiation shield.

We hope to achieve temperatures to 1.6K using this new cell and to obtain additional data

for the density derivative of the structure factor at two temperatures well above and below

the X point.

37
High Resolution Fermi Chopper for Neutron Time of Flight Analysis

Bernard Mozer

(Inorganic Materials Division)

A curved slit Fermi chopper was designed to provide high resolution analysis at the instrument located at BT-5. The new chopper is similar to those currently in use and

consists of aluminum disks bolted together holding a curved slit package of twelve

plates of high strength maraging steel. The steel plates are 1/32" on a curve whose

radius is 37.5 inches. The slits are 0.2 inches apart. The transmission function for this

o chopper is maximum at wX=20,000 rpm-A, or for 2A neutrons and a rotor speed of 10,000 rpm.

The rotor has been tested and was used in an experiment on Polyoxymethylene and to remeasure vanadium as a standard. The vanadium spectrum was quite sharp. The resolution

of the chopper and the flight path is such as to allow 1% resolution at lA for a rotor speed

of 10/000 rpm.

Cold-Neutron Time of Flight Facility

R. S. Carter, A. A. Cinquepalma, L. A. de Graaf, F. J. Shorten, and J. B. Sturrock

The cold neutron time of flight facility is designed for inelastic neutron scattering

studies of solids and liquids. A neutron beam from the reactor is filtered through polyo crystalline beryllium to eliminate neutrons with wavelengths smaller than 3.96A. The beam

then passes through a four rotor phased chopper system which chops the beam into short

bursts of neutrons of selected energy. The sample to be studied is placed immediately

after the choppers and the scattered neutrons are detected in a large bank of detectors

arranged along the arc of a circle with a 2.4 meter radius. The detector information is

fed into a multi-channel analyzer and the neutron energy determined from the flight time

of the neutrons from the sample to the detectors.

The testing of the four rotor phased chopper system has been completed and the choppers

have been installed at the beam hole. The steel framework for the detector shielding room

has been completed and the walls and ceiling are under construction. The multiple detector

bank is ready for installation in the shielding room when it is completed.

A temporary shielded flight path and a single bank of detectors have been installed

to make use of the chopper system while the multiple-detector bank and shielding room are

being completed. This temporary system is currently being checked out.
Cold-Neutron Source

R. S. Carter, E. M. Guglielmo, and L. A. de Graaf

The NBS reactor includes a special port, 22" in diameter, which penetrates the reflector

up to the edge of the fuel elements. This large opening was designed to provide space for

the insertion of a cold neutron source close to the core. By inserting a large, low

temperature moderator it is possible to significantly increase the available intensity of

very low energy neutron (A>4A) which are very useful for many types of molecular dynamic

studies

The moderator will be a cylinder of DO ice 14" in diameter by 12" long. A small

amount of HO may be added to optimize the moderating property of the source. The source

will have a reentrant hole 4" deep by 8" in diameter for beam extraction. The hole will be

filled with beryllium which has the property of reflecting the higher energy neutrons back

into the moderator while passing the lower energy neutrons. The moderator will be

maintained at 25°K by cold helium gas passing through tubing in the moderator. The vacuum

cryostat containing the moderator will be constructed of thin-walled aluminum to minimize

heating by capture gamma rays. The cryostat will be mounted on a shielding plug and the

whole assembly will roll inside a second plug and shield assembly which itself will roll

into the special port of the NBSR. The shield mounted on the second plug surrounds the

cryostat and consists of about 4" of lead and bismuth which grealy reduces the gamma ray

heating of the moderator. Two 6" and two 2" diameter beams can be extracted from the cold

source through the reactor shield. One of the 6" beams will be used for the cold neutron

time-of-flight facility while the others await future development.

The helium for cooling is provided by an all helium refrigerator using a turbine

expansion engine developed by the NBS cryogenic laboratory in Boulder. It has a one kilowatt

capacity at 25°K which is sufficient to handle the heat generated in the moderator at twice

the current reactor power.

The bismuth tip and the cryostat are the only items which remain to be installed. The

cryostat has been received and extensive testing has just started. Of particular concern is

the testing of the procedure for freezing the ice moderator in the cryostat without damaging

it. The method consists of freezing the water in layers from the bottom up to prevent a

thick layer of ice from forming over the freezing water. To make this possible the cryostat

39
has a water filled tube which is well enough insulated to use even after several layers of

water have been frozen and the cryostat is quite cold. This procedure has been checked in a

full scale mockup and refinement of the procedure is continuing.

The bismuth tip which was expected some time ago failed to pass its inspection at the

plant. It had to be reworked and should be ready for another acceptance test shortly.

The installation procedures and the inplace testing program are being developed.

After thorough testing, including measurements of radiation induced gas releases in the

moderating material itself, application will be made to modify the technical specification

so that it may be used at low temperature

40
Publications

"A Time-Shared Computer System for Diffraction Control", H. A. Alperin and E. Prince,

NBS J. of Res., Sec. C. , 74C 89 (Dec. 1970).

"The NBS Reactor as a Source of Neutrons", R. S. Carter, Proc. of the ANS Topical

Meeting on Neutron Sources and Applications, Augusta, Ga. , 2_, 1-10 (April 1971)

"Structure Study of Liquid Neon by Neutron Diffraction", L. A. de Graaf and B. Mozer,

J. Chem. Phys. (in press)

"Refinement of the Crystal Structure of Apophyllite. II. Determination of Hydrogen

Positions by Neutron Diffraction", E. Prince, The American Mineralogist 56_, 1243 (JulyAug. 1971) .

"The Structure of Ammonium Nitrate (IV)", C. S. Choi, J. E. Mapes , and E. Prince,

Acta Crysta (in press)

"Study of Hindered Rotation in Crystals by Neutron Transmission Measurements:

Comparison of Calculated and Measured Scattering Cross Sections, J. Chem. Phys., P. S. Leung,

J. J. Rush, and T. I. Taylor (submitted to J. Chem. Phys.) .

"Neutron Diffraction Study of the Structure and Thermal Motion of Phosphonium Bromide"

L. W. Schroeder and J. J. Rush, J. Chem. Phys. 3_4, 1968 (March 1971) .

"Quasielastic Neutron Scattering by Hydrogen in the a and 6 Phases of Vanadium

Hydride", J. M. Rowe , K. Skold, H. E. Flotow and J. J. Rush, Phys. and Chem. of Solids 32 ,

41 (April 1971)

"Neutron Diffraction Study of the Trigonal and Cubic Phases of NaSH" , L. W. Schroeder,

L. A. de Graaf, J. J. Rush, J. Chem. Phys. (in press)

"The Dynamics of Sodium and Potassium Bifluoride: Infrared, Raman and Neutron Studies",

J. J. Rush, L. W. Schroeder and A. J. Melveger, J. Chem. Phys. (in press)

"The Crystal and Molecular Structure of Hexakis (imidazole) cadmium(II) nitrate,

[Cd( HN ) 2(N0 ) and Hexakis (imidazole) cadmium (II) hydroxide nitrate tetrahydrate,

[Cd(C H N ) ] (OH) (NO ) -4H 0" , A. D. Mighell and A. Santoro, Acta Cryst. (in press).

"Properties of Crystal Lattice: The Derivative Lattices and Their Determination",

A. Santoro and A. D. Mighell, Acta Cryst. (submitted for publication)

"The Crystal and Molecular Structure of the 2:1 Dimer Dibromobis (Pyridine N-oxide)

Copper(II) [Pyridine N-oxide) CuBr] " , A. D. Mighell, C. W. Reimann, A. Santoro, Acta

Cryst. (in press)

41
"The Crystal and Molecular Structure of Nitratobis (dipyridine) Cobalt (III) Hydroxidenitrate Tetrahydrate , [CofC^HgN^

2 <N03

) ] (N0

3

> (OH) -4H 0" , C. W. Reimann, M. Zocchi,

A. D. Mighell and A. Santoro, Acta Cryst. (in press)

42
B, Interagency Collaborative Programs

Spin Structure of Erbium in High Magnetic Fields

J. J. Rhyne and S. J. Pickart

(Naval Ordnance Laboratory, White Oak, Md.)

The rare earth metals display a wide variety of magnetic spin states or structures

depending upon a delicate balance of exchange, anisotropy and magneto-elastic interactions.

The inter-dependence of exchange and anisotropy energies is not well understood, particularly in erbium. The results of high field magnetization experiments are complex and are

not readily interperable without additional information. This requirement provided the

motivation for a direct examination of the spin structure evolution in Er with fields up

to 60 kOe and temperatures from 4K to 60K using the newly developed superconducting

magnet facility.

The zero field spin state of erbium at 4K is a conical ferromagnet in which ferromagnetic order exists along the c crystal sxis with concomitant helical order of the basel

plane moment component. Our studies show the resulting cone angle to be 30 degrees in zero

field in accord with previous determinations . The periodicity of the helical order is not

commensurate with the lattice and has a value x = . 24c* . This wavevector remains unchanged

to 60 kOe applied fields

A computer program was developed which allows the automatic scanning and location of

satellite and fundamental reflections along a prescribed path in reciprocal space.

A typical scan along the c axis using the arbitrary scan program is show in Fig. 1.

The trajectory was from (112) to (112) in reciprocal space. The program automatically

identifies peak positions during an initial coarse scan, then refines their exact coordinate,

and finally executes a traditional 2:1 scan over each peak to permit comparison of

integrated intensities.

The erbium results of Fig. la show the expected twin satellites of each principal

nuclear peak arising from the helical order. Application of a magnetic field above 17 kOe

along the [100] direction collapses the conical order as manifested by the dramatic

± + decrease in (100 ) and 112-) satellite intensities as shown in Fig. lb for data at 60 kOe.

Such a transition to a stable of lower free energy results from the competition of

exchange anisotropy and applied field energies. Analysis of the data has shown that the

43
high field state is a "fan-type" moment structure. The angular width of the "fan" was

observed to decrease with increasing field reaching 45 degrees at 60 kOe. The c axis

moment component remains constant at 7.5 u during the magnetization process. The moment

6 associated with the fundamental (ferromagnetic) component of the fan structure is 3.8 u . B Harmonic satellites of all orders are theoretically possible with this structure; however

those above first order were below our detection sensitivity. The data for the field

dependence of the spin structure are to be evaluated in a theoretical model to obtain

magnetic anisotropy and exchange energy information.

44
300 -

200-

100

Jwj

H-0 3660

il. A . j. . .^ ..j^. i. ...A JiLJv—

i

2000

ERBIUM 4.2K

lit SCAN

H =

JL~. is. li VJ Vg

A

1200 ERBIUM

1 *

2 00! SCAN

E H-0

E 800

3

E

E3 400 "

"jlJ uI

2.0 1.0 0.0

I

1.0 2.0 1.6 2.0

/

2.4

Pig. la. Abritrary reciprocal space scan a parallel to the c axis in erbium at 4K.

Each allowed nuclear reflection is observed to have symetric first order

magnetic satellites produced by the helical order. Magnetic intensity is

also present on all nuclear reflections (except ooZ) from the c axis ferromagnetic moment.

Note: Nuclear reflection amplitudes are truncated for clarity.

\ 2050 ERBIUM 4.2K

II t SCAN

H=60 kOe

H II pOO]

300 B J2000

200 "9

3340 1

- 9 100

**K~J LJL. j-_ . V

n r~A^ »--wl _ 1 *- J V^T-~*"w«yL. .i——s.-.^JK^^ , A J Ix,

o 100-

B

ERBIUM

4.2 K 004SC4N

H»60k0e

H II [lOO]

A , UJ

2.0 •1.0 0.0

I

1.0 2.0 1.6 2.0I

2.4

Fig. lb. A similar scan at 4K with an applied magnetic field of 60 kOe along [100]

.

The satellite intensity is severly suppressed due to the development of a

"fan" moment strucutre as discussed in the text. The < 111 > reflections

are a result of double Bragg scattering.

45
Rare Earth Lead Salt Magnetic Semiconductors

J. J. Rhyne

(Naval Ordnance Laboratory, White Oak, Md.)

A new study was undertaken of the doping of lead^salt, narrow-gap semiconductors with

local moment rare earth ions. Such materials when ordered are known as magnetic semiconductor properties (e.g. resistivity and optical band gap) by externally applied

magnetic fields. We have used elastic neutron scattering to study the magnetic state of

Gd-doped PbTe and SnTe using a powder dispersal method to reduce the effective Gd crosssection. Initial studies on 10% doped material showed no evidence of long range order to

2K. Work is presently underway using silver additions to the material to raise the

effective carrier density and hence favor ordering by the indirect exchange process.

Neutron investigation will be used to search for antiferromagnetic and periodic moment

states whose detailed nature cannot be obtained by other methods.

Rare Earth - Cobalt Intermetallic Compounds

J. J. Rhyne and H. A. Alperin

(Naval Ordnance Laboratory, White Oak, Md.)

The magnetic structure of compounds of rare earths with cobalt is being examined

throughout their range of magnetic order. Measurements to above 1000 K have been made

using a modified high temperature vacuum furnance originally built for work on liquid

aluminum. Principal compounds studied were of the RE Co _ and RECo structures.

The neutron analysis allows the separation of the temperature dependence of the

rare earth and cobalt sublattice magnetization. Of interest here is the possible modification of the rare earth exchange interaction by the presence of the cobalt.

Initial results on Tb Co confirm a ferromagnetic structure with a Cobalt Curie

temperature near 800 K. A set of analysis programs is being developed to perform the

decomposition of Co and rare earth moment dependences. TbCo has an atomic arrangement

quite similar to that of Tb Co _ . Neutron scans show, however, an unexpected antiferromagnetic moment component and a Curie temperature only a few degrees above room

temperature. Additional investigations are planned of a series of other rare earthcobalt and rare earth-iron intermetallic compounds.

46
Structural Studies of Amorphous Solids

by Neutron Diffraction

G. A. Ferguson, J. Konnert and J, Karle

(U.S. Naval Research Laboratory, Washington, D.C.)

The interagency collaborative study between the Laboratory for the Structure of

Matter, U.S. Naval Research Laboratory and the Reactor Radiation Division, National

Bureau of Standards to determine the structure of amorphous solids of interest in modern

technology has included a precise measurement of the diffraction spectra of silica,

germania and vitreous arsenic selenide.

Previously published discrepancies appearing in reports of structural studies of

silica, using the neutron and x-ray diffraction techniques, have been investigated and

explained as part of an effort to understand this basic representative of the vitreous

state. This understanding has been obtained through newly devised data reduction

procedures applied to precisely measured diffraction data obtained over an extended

range of momentum change of incident particle (neutron and photon) . These procedures

have revealed an ordering in the vitreous specimen which is greater than heretofore

suspected. A new interpretation of the structure of vitreous silica has been developed

which is based on maxima which occur in the radial distribution curve beyond 10A. This

interpretation suggests that when vitreous solids are formed, certain crystalline-like

arrangements of their atoms appear over limited spatial regions of the specimen. This

region, which was previously considered to be less than 5A for silica, is approximately

twice as large as reported by other investigators . The ordered arrangement is characteristic of the vitreous state and is not to be considered as indicative of a partially

crystalline specimen.

The data reduction techniques which have been developed and applied successfully

in the silica are being employed to interpret new diffraction data obtained for germania

and vitreous arsenic triselenide.

47
The Lattice Dynamics of NaNO,

K. W. Logan and S. F. Trevino

(Picatinny Arsenal, Dover, N. J.)

and

R. C. Casella

and

W. M. Shaw and J. D. Muhlestein

(University of Missouri, Columbia, Mo.)

and

R. D. Mical

(Massachusetts Institute of Technology

Cambridge , Mas s .

NaNO crystallizes in a rhombohedral unit cell with two formula units in the primitive

cell. Most of the dispersion curves have been measured in the high symmetry A direction

and some in the lower symmetry A and B directions . The assignments of the observed T

phonons was accomplished by the use of group theoretical selection rules developed by

R. C. Casella and S. F. Trevino (see Casella and Trevino, Division Programs, Sec. A).

These techniques proved invaluable in determining the reciprocal lattice point to use

in observing the various phonons. The measurements resulted in a unification of the

infrared and Raman assignments and the observation of the two V phonons which are

optically inactive. In addition, a comparison with the results of a shell model calculation which successfully reproduced the observed optical data shows that it does not

correctly predict all of the neutron measurements. The paper has been presented at the

"International Conference on Phonons" and will be published in the proceedings of the

conference.

48
The Structure of Ammonium Nitrate (IV)

E. Prince

and

C. S. Choi, and J. E. Mapes

(Explosives Laboratory, Picatinny Arsenal, Dover, N. J.)

The structure of ammonium nitrate (IV) , the phase which is stable between -18°C and

32. C, has been refined by least-square methods with three-dimensional neutron diffraction

data. Of 188 independent reflections, 29 were too weak to observe with sufficient

accuracy, and 4 were affected by severe secondary extinction. The remaining 155

reflections were used in the refinement with anisotropic temperature factors and an

isotropic extinction parameter. The final weighted R index was 0.028. The structure

o o o shown in Fig. 1, is orthorhombic ji = 5.745A, b = 5.438A, £ = 4.942A, space group Pmmn,

with two NH NO formula units per unit cell. The ammonium and nitrate groups both occupy

positions with mm symmetry. They are bound together by a two-dimensional network of

hydrogen bonds, forming infinite sheets parallel to (001). The hydrogen bonds involve only

one vertex of the triangular nitrate group, so the group is almost free to rotate around

an N-) bond. Phase II, the tetragonal phase which is stable from 84.2°C to 125. 2°C, is

formed by a rotation around this bond. Phase III is stable from 32.3 6 C to 84.2°C, but

both phase II and phase IV are metastable with respect to it. It is formed from phase IV

by breaking the infinite sheets into double chains, followed by slight repacking.

Fig. 1. stereo pair showing the structure of ammonium nitrate, viewed along the b axis.

HSf
Precision Measurement of the Thermal Neutron

Scattering Amplitude for Silicon

C. S. Schneider, U. S. Naval Academy

The narrow wavelength bands of neutrons passing between two parallel perfect crystals

include higher order wavelengths to the extent passed by the quartz filter at the reactor

face. These neutron beams are simultaneously refracted by a right prism of silicon between

the crystals, yielding an angular separation of the first and third orders to the second,

or analyzer crystal:

2 Ae

8 NXb

[tan ^ + cQt ^

where N is the atomic density, A is the primary neutron wavelength, and <j> is the angle of

the prism surface from the beam. The refraction peaks are shown in Fig. 1.

The beam port and counting electronics have been completed. The double perfect crystal

spectrometer has been constructed as shown in Fig. 2, with calibrations completed for

(1) the wavelength slits (first order)

X{A) = 3.149 95(6) + (. 250-y) 0.0191

where y is the slit center position in inches.

(2) the refractive goniometer:

arc

sees)

I m i.337i( 2 )y - 0.036 \^r\ I 10 I

where y is the computer angle in revolutions of the drive motor. This calibration is still

under study.

(3) the prism goniometer:

(rads) = 0.348 675(7) (y- .2868) ! +

(y- ,2868) 2 (y- .4743)

141.54

where y is the micrometer reading in inches.

One refractive separation has been measured and shows reproduceability within at least

one part in 5000.

50
•H

ro <nj —

51
CNH

fa

0) 1 c a c <D £ GQ

X) co

(1) 3

1£ a> en 2r ecu:

52
Equipment Development; NBS-NOL-NRL Joint Program

H. A. Alperin, J. J. Pickart, J. J. Rhyne and R. H. Williams

Naval Ordnance Laboratory, White Oak, Md.

V. J. Minkiewicz

University of Maryland, College Park, Md.

1. Triple-Axis Neutron Spectrometer

A three axis neutron spectrometer was completed and tested during the past year.

Preliminary measurements have been made of phonons in PbTe at room temperature with an

extension to low temperatures in progress. Initial results from the spectrometer indicated

a need for additional shielding to reduce the background level to the range of one count

per minute. This was accomplished with temporary facilities pending the completion and

installation of a permanent shield late in 1971. Modifications have also been made to the

counter and associated electronics to reduce noise and background.

2. Superconducting Magnet

A split-pair superconducting magnet and associated temperature-controlled dewar were

completed, tested and used for the initial experimental investigation of the high field

magnetic state of the erbium. The system performed well showing reasonable stability in the

persistent operating mode and a field uniformity better than one percent over the width of

the neutron beam. Helium losses from lead heating and thermal conduction were found to be

minimal. One coil of the pair was found to have a low-resistance joint in the superconducting tape which precluded its operation above 60 kOe. This is in the process of being

repaired and on completion the solenoid is expected to produce the full 100 kOe design field.

3. High Temperature Furnace

A vacuum furnace originally designed and used for a study of liquid aluminum was

modified to accept conventional powder and single crystal specimens. Temperature stability

was improved and an accurate calibration was performed to temperatures up to 1500 K.

53
Equipment Development; NBS-Picatinny Arsenal Joint Program

C. S. Choi, H. J. Prask and S. F. Trevino

Explosives Lab, Picatinny Arsenal, Dover, N. J. and

J. J. Rush, R. S. Carter and A. Cinquepalma

The interest of the PA group has been the study of the structure and lattice dynamics

of metastable and related materials, primarily by means of neutron scattering, with the aim

of elucidating the cause of instability. Considerable effort has also been devoted to the

study of stable materials such as polymers, hydrogen-bonded systems, ionic and molecular

solids, molecular liquids, crystal hydrates and metal hydrides. The activities in the

collaborative program began in September 1970 after the shutdown of the Army reactor at

Watertown, Massachusetts.

The main effort of the collaborative program at NBS, thus far, has been the design and

fabrication of new shielding and components for instruments used at Watertown. These

instruments include a conventional triple-axis spectrometer and a neutron diffractometer.

To achieve higher efficiency in neutron utilization, both of the above instruments will be

mounted on a single beam-port. The neutron diffractometer will employ a thin aluminum

single-crystal monochromator , and the three-axis instrument will utilize the neutrons

transmitted by the diffractometer monochromator. Because large single crystals for coherent

neutron inelastic scattering measurements are often difficult to obtain, considerable effort

has been devoted to maximizing signal/background levels through shielding improvements. Two

such improvements are a 360° counter-analyzer shield, fixed with respect to the scattered

beam, in which the counter and analyzer are housed, and a fixed shield, circumferential to

the main monochromator shield, which allows variation of incident energy without movement

of shielding.

An existing fixed-crystal-monochromator, time of flight spectrometer will be mounted on

a second beam tube along with a second three-axis instrument. The time of flight instrument

incorporates a relatively simple mechanical phasing system between a coarse chopper - for

order elimination and background suppression - and a "fine" Fermi chopper. Incident neutron

burst times of 20-25 ys are obtained with this system.

The present status of the above-described development is the following. The

diffractometer/triple-axis system is essentially completed, with fabrication of only a few, 54
relatively simple, shielding components remaining. Installation and operation is expected

to be achieved in the next quarter. Modifications of the time of flight instrument are near

to completion. A new support system for the five-meter flight path is being tested, and a

modification of the chopper phasing control has been designed. New shielding - very little

of which will be required for this instrument - is being designed. The second triple-axis

instrument is in the conceptual design stage.

55
Publications

"The Lattice Dynamics of NaN03

" , K. W. Logan, S. F. Trevino, R. C. Casella, W. M. Shaw,

L. D. Muhlestein and R. D. Mical, to be published in "Proceedings of the Conference on

Phonons", Rennes, France, July 1971.

"Ice I - Lattice Dynamics and Incoherent Neutron Scattering", H. Prask, S. Trevino,

J. D. Gault and K. W. Logan, submitted to J. Chem. Phys.

"Lattice Dynamics of Rhombohedral Sodium Azide", H. Rafizadeh, S. Yip and H. Prask,

J. Chem. Phys., (in press).

"The Lattice Dynamics of KN 3 ", K. R. Rao, S. F. Trevino, H. Prask and R. D. Mical,

Phys. Rev., (in press).

56
C, Non-Division MBS Programs

Measurement of Avergae Fission Cross Section Ratios

James A. Grundl

(Nuclear Radition Division)

A cavity fission neutron source at the reactor thermal column has been operated in

conjunction with a fission ionization chamber to measure average fission cross section

— 235 — 238 ratios. The ratios, a ( U) /a ( U) , have been measured for U-235 and Pu-239 fission

neutrons. The cavity fission source, a single fission ionization chamber, and a redundant

determination of fission foil weight ratios were employed for the measurements. The result

for t>-235 fission neutrons is 3.81+0.17, a value which confirms earlier integral microscopic

measurements and remains discrepant with predictions based on differential microscopic

data to the extent of 10 to 17%. The measured ratio of average cross section ratios,

X c /X-,-)q' is 0.970+0.012. This value represents a departure from unity which is less

than one-half that predicted by differential microscopic data. A paper describing these

measurements was presented at a consultant's meeting, "Status of Prompt Fission Neutron

Spectra", called by the Nuclear Data Center at the IAEA in Vienna. Refinement of these

measurements is continuing

Quality Assurance Irradiations for Fast Reactor Materials Dosimetry

W. N. McLroy, L. S. Kellogg, and W. Y. Matsumoto

(Dosimetry Center of the Hanford Engineering Development Laboratory)

Rabbit irradiations in the RT-4 pneumatic facility of the NBS reactor were performed

with materials used for high flux, neutron fluence monitors by the Fast Reactor Materials

Dosimetry Center (FRMDC) at the Hanford Engineering Development Laboratory (HEDL) . The

primary objective of these irradiations was quality assurance; in particular, the determination of the concentration and homogeneity of gold, silver, and tantalum in alloys of

aluminum. A secondary objective was the search for small thermal and resonance energy

63 54 47 cross sections in the exoergic threshold reactions Cu(n,cO , Fe(n,p) , Ti(n,p) , and

583°Ni(n,p).

57
Arrangements for carefully positioning a multiplicity of small wires and foils, and

also development of a technique for heat removal which made possible exposures with

cadmium covers, were notable characteristics of the irradiations. The neutron flux for

each irradiation was monitored with Au-Al and Co-Al activation detector wires; the

latter is an NBS Standard Reference Material (SRM) . The flux level and cadmium ratios given

by the monitors for the RT-4 position were

(nv) . = 1.26 x 10 (reactor at 10 MW) tn cadmium ratio for Cobalt = 368 (infinite dilution)

cadmium ratio for Gold = 38 (infinite dilution)

The necessity for such quality assurance irradiations was amply demonstrated. The

silver and gold concentrations determined for the alloys differed by more than 50% and the

tantalum alloy by 10% from the values certified by the vendor . The new values , obtained

from the RT-4 irradiations, are based on comparisons with reference standards as well as

on the NBS standard reference Co-Al wire and thermal neutron cross section values. The

value for the Au-Al material was additionally verified by three independent analytical

measurements. Needless to say, the reliability of this SRM is of considerable important

now for the Fast Reactor Dosimetry Center at HEDL.

58
Activation Analysis Section: Summary of Activities FY 1971

P. D. LaFleur

Analytical Chemistry Division

The Activation Analysis Section of the Analytical Chemistry Division is physically

located in the NBS Reactor Building. A complete description of the Section's activities

may be found in its annual progress report, NBS Technical Note 588, therefore only a brief

summary will be included here.

1. Biological Standard Reference Materials

In addition to a comprehensive analytical program on two new Biological Standard

Reference Materials, SRM 1571, Orchard Leaves and SRM 1577, Bovine Liver, Section personnel

were responsible for the overall coordination of the analytical program for these important

standard materials throughout the Analytical Chemistry Division. The first of these materials

SRM 1571, was issued during the year and is certified for three major constituents, two

minor constituents and 14 trace constituents. In addition, preliminary values were given

for another 9 trace constituents. These materials are designed to give scientists working

in the areas of nutrition, metabolic disease and pollution, as well as analytical chemists,

materials which closely approximate the matrices with which they are concerned. The

certification of these standard materials was a painstaking process so that the scientific

community may be assured of the accuracy of the results obtained. As an example, the

certified value for mercury in the orchard leaves was obtained only after approximately one

man year of analytical effort had gone into this analysis in the Division.

Concurrent with the analysis of these materials, a program has been inaugurated to

accurately determine the pressure buildup of a variety of organic materials upon irradiation

in a nuclear reactor. Differences between pressure buildup in freeze-dried and nonfreezedried materials and as a function of fast to thermal neutron ratios are being pursued. Thus

far over 100 samples have been irradiated and tested for pressure buildup inside a quartz

ampoule using a water monometer system.

2. Mercury Analysis

Considerable effort was expended during the year on the development of a destructive

analytical technique for determining mercury in biological matrices. The method consists of

burning the sample after irradiation in an oxygen stream and trapping the mercury and other

volatiles in a liquid nitrogen cold trap. Extensive testing for chemical yield was performed.

59
It was determined that the procedure is quantitative and that using high resolution

lithium-drifted germanium solid state detectors, mercury may be determined at levels of

approximately one part per billion without great difficulty. Using the procedure developed,

mercury was determined in the orchard leaves and bovine liver Standard Reference Materials

and Standard Reference Material 1630, Mercury in Coal. The Section also participated in a

round robin analysis of mercury in coal sponsored by the United States Bureau of Mines.

3. Californium-252 Neutron Source

The use of Californium-252 neutron sources was investigated during the year and a

procedure was developed for the determination of fluorine using the nuclear reaction

9F(n,a) N. The procedure was applied to a number of fluorine containing organic materials

with excellent accuracy and precision. In addition, hafnium was determined in zircoloys

using the reaction Hf(n,y) Hf. Additional work is being done in the determination of

macroconstituents in Standard Reference Material Metallo-organic compounds to evaluate high

precision activation analysis using a stable neutron source such as californium-252.

4

The Nuclear Track Technique

The nuclear track technique has been applied to the determination of nitrogen and

lithium in biological materials using protons from the reaction nitrogen l%I(n,p)14c ^n ^e

case of the determination of nitrogen and alpha particles from the reaction ^Li(n,p)^He for

the determination of lithium. Investigations are continuing for the application of this

technique to the determination of thorium in geological and glass samples using a fast

neutron, thermal neutron differential technique to correct for possible uranium contribution.

5. Mass Separator

A high throughput mass separator has been installed in the Section and its applications

to activation analysis and nuclear chemistry are being evaluated at the present time.

Resolution, yields and "memory" are being studied for the application to particularly

difficult problems in activation analysis where an interference free source must be obtained.

A separation by atomic number may be performed using chemistry and separation by mass

number subsequently performed using the mass separator. In this way it is possible to

obtain a pure isotope for radiation detection.

In addition to the subjects discussed above, the Section has participated in a large

number of analyses for other Sections in the Division and other Divisions at the Bureau and

60
for other Federal Agencies. Work is continuing in the application of computer techniques to

activation analysis and specifically in an interactive system using a minicomputer and multichannel pulse height analyzers . Work has also begun on the methods for the determination of

a number of other toxic metals in tissues and foodstuffs, for example selenium, cadmium, and

arsenic, and this effort will be continued during the coming year along with a number of

fundamental studies in the activation analysis technique.

Atomic Constants from x-ray and Positronium Decay y~raY Measurements

R. D. Deslattes and W. C. Sauder

(Optical Physics Division)

The development of the necessary instrumentation for this experiment has continued

during the past year and shortly will be installed in the controlled environment chamber

in the reactor building.

Cobalt-60 Nuclear Thermometry

H. Marshak and R. J. Soulen, Jr. (Heat Division)

The degree of orientation of a nuclear spin system is defined in terms of the populations am of the nuclear energy levels Em by the Boltzman factor, viz

e-EmAT

l e-Em/kT

m=-I

where I is the nuclear spin with projection m, k is the Boltzman constant and T the absolute

temperature. A measurement of these populations would enable us to determine the absolute

temperature. The accuracy would depend upon the accuracies of Em , k and the measurement of a^ Since the energies E^, are usually quite small - the order of fractions of a degree -

such a thermometer is only useful at very low temperatures.

The populations am can be determined by measuring the angular distribution of Y -r ays

from a radioactive sample. If the multipolarity of the transition and the initial and final

states involved are known, the anisotropy of the radiation can yield the absolute temperature.

61
A very favorable case is now being investigated; namely Co-60 in a hep Co-59 single crystal.

The Co-60 nuclei are produced in_ situ by irradiating the small Co-59 single crystal in the

NBS reactor.

A preliminary comparison has been made of this thermometer and a Josephson Junction

Noise Thermometer over the temperature range of 20 to 40 mK. The results showed agreement

to within +_ 0.5 mK. Further measurements are planned in order to improve the accuracy.

Decay Scheme Studies

F. J. Schima

(Nuclear Radiation Division)

Sources of Xe^l29m have been prepared using the isotope separation at the CRR and the

NBS reactor. Xe-128 was ion implanted into ultra pure Al foil. The foil was trimmed down

to a strip, 4 mm x 2.5 cm and irradiated in RT-4 for 8 hour periods. The gamma activity

was then observed by Si (Li) and Ge(Li) detectors. The energy of the isomeric transition

was measured as 196.38 + .11 keV, and the energy of the first excited state, as 39.50 +_ .17

keV. The half-life of the 235.88 keV level was observed by the 196.38 keV gamma ray

and was measured to be 8.87 + .09 days. This is considerably greater than the 8.0 +_ .2 day

value adopted by the literature.

A source of Kr-81 was prepared by irradiating 7.6 ml sample of Kr gas (enriched to

50% Kr-80) in G-2 of the NBS reactor for 8 weeks. After a 6-month cool down, the gas was

implanted in Al foil using the isotope separation. A gamma ray was found and its energy

was measured to be 275.99 +_ .01 keV. The K x-ray intensity was measured by an intercomparison to the standard sources of Co-57 and Se-75. The ratio of the 275.99 keV gamma

ray intensity to the K x-ray intensity was determined to be 6.8 + .8%. This would indicate

a branch to the first excite state of Br-81 of approximately 3.7%, depending on the value

of the fluorescent yield that is taken. This branch in the Kr-81 decay has not been

previously reported.

Preliminary work has been done on a measurement of the fission yields of Xe-131m and

Xe-129. A noble gas handling system has been built and is undergoing tests. Several 2 mg

235

U

3 Og samples have been irradiated in RT-4. it has been estimated that a 30 minute

irradiation would be least sensitive to the ingrowth of Xe-131m from 1-131 decay and yet

produce a detectable amount of Xe-131m from fission.

62
Parity Violation in Strong Interactions

J. L. Alberi and R. Wilson

(Harvard University, Cambridge, Mass.)

and

G. Scharff Goldhaber

(Brookhaven National Laboratory)

and

I. G. Schroder

(Nuclear Radiation Division)

The' program to study parity violation due to the weak interaction in the overall

nucleon-nucleon interaction (weak forces between nucleons) is continuing in collaboration

with Harvard University and Brookhaven National Laboratory.

Preliminary data with a Cd-113 target has been obtained and a control experiment

with an internal titanium target is underway. A search is being conducted for other

nuclei which have neutron capture states which are no longer eigenstates of parity and,

therefore, exhibit small parity impurities similar to those in cadmium.

Two-Photon Emission in (n,p) Capture

B. T. Chertok

(American University, Washington, D.C.)

and

J. L. Alberi

(Harvard University, Cambridge, Mass.)

and

I. G. Schroder

(Nuclear Radiation Division)

A search for two-photo emission in thermal (n,p) capture has been conducted with the

aim of establishing a lower limit to the occurence of this phenomenon. The data both

with a hydrogen (HO) and a deuterium (DO) target has been obtained and the data is being

analyzed.

63
3 Fast Neutron He Spectrometer

E . D . McGarry

(Nuclear Vulnerability Branch - HDL)

and

I. G. Schroder

(Nuclear Radiation Division)

In collaboration with HDL a program is underway to extend the region of application of

the He- 3 fast neutron spectrometer below the 500 KeV region by means of fast electronics

and shaping circuitry to help eliminate the low-energy y -ray sensitivity of the semiconductor spectrometer. Several circuits have been used and y-charged particle

discrimination obtained in the 500 KeV region. Several tests have been performed with a

Cf-252 source on loan from Savannah River (AEC)

64
Publications

"Production and Certification of NBS Biological Standard Reference Materials"

,

D. A. Becker and P. D. LaFleur, Proc. of the 4th Annual Conference on Trace Substances in

Environmental Health, Columbia, Missouri, June, 1970.

"Neutron Activation Analysis: Applications to Trace Element Analysis in Biological

and Environmental Materials", D. A. Becker and P. D. LaFleur, Proc. of the 5th Annual

Conference on Trace Substances in Environmental Health, Columbia, Missouri, June 1971

(in press)

.

"SRM Biological Standards: Filling a Need", D. A. Becker, P. D. LaFleur and

T. W. Mears, American Industrial Hygiene Journal (in press).

"Determination of Trace Concentrations of Boron and Uranium in Glass", B. S. Carpenter,

Anal. Chem. (in press)

.

"Observation of Proton Tracks in Cellulose Nitrate", B. S. Carpenter and P. D. LaFleur,

(Submitted to J. Appl. Rad. and Isot.).

"Quantitative Applications of the Nuclear Track Technique", G. S. Carpenter, Proc.

of the International Microchemical Conference (in press)

.

"Activation Analysis Section: Summary of Activities, July 1969 to June 1970",

Philip D. LaFleur and Donald A. Becker, NBS Technical Note 548.

"Gamma Ray Spectroscopy", P. D. LaFleur and B. A. Thompson, Encyclopedia of Chemistry,

(in press)

.

"Activation Analysis: A Bibliography", G. J. Lutz, R. J. Boreni, R. S. Maddock and

W. W. Meinke, NBS Tehn. Note 467 (May, 1971).

"Determination of Lead in Environmental Samples by Photon Activation Analysis",

George J. Lutz, Proc, ANS Topical Meeting, Nuclear Methods in Environmental Research,

Columbia, Missouri (in press)

.

"Determination of Thallium by Photon Activation Analysis", L. W. Masters and

G. J. Lutz, Anal. Chem. Acta (in press)

.

"Determination of Trace Elements in Ruby Laser Crystals by Neutron Activation

Analysis", Barbara A. Thompson and Eric C. Miller, J. Res. NBS - A. Physics and Chemistry,

75A, No. 5 (1971)

.

65
"Characterization of Ancient Bronze Artifacts by Neutron and Photon Activation

Analysis", Barbara A. Thompson and George J. Lutz (Submitted to Science).

"Computer Data Reduction in Activation Analysis", Herbert P. Yule, Proc. of the NATO

Advanced Study Institute Activation Analysis in Geochemistry and Cosmochemistry , Kjeller,

Norway (1971)

"A Conversational Text Editor for a Laboratory Minicomputer", H. P. Yule,

Anal. Chem. (in press)

"A Study of Gamma-Ray Spectrum Distortion by Mathematical Smoothing", H. P. Yule,

(Submitted to Anal. Chem.).

66
REACTOR OPERATIONS AND SERVICE PROGRAMS

A, NBSR Operating Summary

During the period October 1, 1970 through September 30, 1971, approximately 5100 hours

of reactor time was provided to users. This is equivalent to about 51,000 megawatt-hours of

energy produced. Operational problems discussed below and operations with minimum staffing

reduced reactor on-line time to 58% for this period compared with 67% last year. Significantly

improved average fuel burnup of 48% was achieved through utilization of heavier loaded

elements. A summary of operating statistics together with those of the previous year for

comparison are presented in the following table

NBSR Operating Summary

Reactor operations to date, Mwh

Reactor Operations for year, Mwh

Hours Reactor Critical

No. of Days at 10 Mw

On-line time at 10 Mw

Number of fuel elements used

Average U-235 Burnup

Number of Refueling Operations

Number of Unscheduled Shutdowns

Number of Irradiations

Number of Visitors

Four operational problems of significance were experienced over the last year. These

problems collectively contributed to operating time losses of about four months. Some of

this lost time was made up by reducing the number and frequency of subsequent scheduled

shutdowns through advance performance of required maintenance operations. These problems

are summarized below:

Nov. 1969 Oct. 1970

to to Nov. 1970 Oct. 1971

78213 .3 123760.6

59186,.0 51175.3

6000 5440

247 213

67% 58%

44 24

34% 48%

11 6

3 10

1500 3000

4000 4000

67
1. Repair of Primary System Piping Welds

A small crack developed in each of two welds on small 1/2" drain lines in the primary

cooling system. Difficulty was experienced in rewelding the lines because they were aluminum

and old. In the process a 12" aluminum line had to be capped. Since all repair welds had

to be made to code, a welder had to be qualified and qualification welds prepared. The

final weld had to meet code requirements of inspection including 100% x-ray. Operating time

lost was approximately 22 days.

2. Failure of Primary System Inlet Strainer Basket

The inlet strainer was opened to repair a leaking vent line at which time, it was

discovered that the entire wire mesh screen, two retaining bars and pieces of the bottom

plate had apparently torn loose from the strainer basket and had been washed downstream. The

search for the missing pieces required removal of the core into the storage pool and draining

of the vessel and primary piping. The entire area between the strainer were either visually

inspected or radiographed when visual inspection was not possible. Almost all of the missing

pieces were located and recovered intact. A few small pieces of the base could not be

accounted for but were definitely excluded from the area of concern. It is possible that

these pieces were removed from the basket during previous repairs prior to the operation of

the reactor. New strainers fabricated of heavier materials were installed in both the inlet

and outlet pipes (the outlet strainer was found intact) . The new basket is recessed farther

from the pipe entrance permitting about 2-1/2 times the flow area and reducing the pressure

drop across the wire mesh. Total operating time lost was about 30 days.

3. Failure of the Locking Bar Pins of the Fuel Element Head Assembly

During fuel reloading operations, two fuel elements were dropped in the transfer chute.

In both the fuel element head shaft separated from the locking bar by a type 410 stainless

steel roll pin. The roll pin purchased to Mil-STD 16562 is a 0.131" to 0.135" and is

pressed into a hole that is 0.125" to 0.129" in diameter. Subsequent examination indicated

that the two pins in question were either initially undersized or have become undersized

during installation or use. Both pins fell out and were recovered intact. They measured

0.125" and 0.126" respectively while the holes in the shaft measured 0.127". As a result of

this, fuel element heads were modified by replacing the type 410 stainless steel pin with a

bigger type 304 stainless steel #3 taper pin that is pressed in so that it is below the

68
surface of the bar. The pin is then staked to positively secure it in place. Operating

time lost was about 10 days.

4. Leaks in the Primary System Main Heat Exchanger

Two separate leaks developed in the primary system main heat exchanger within a short

time of each other. In each case the leak involved a single tube. One leak was due to local

corrosion from the outside of the tube, the other was caused by the tube rubbing against a

baffle. Very extensive examination, testing and inspection of the heat exchanger was

performed since there is no backup exchanger. The results indicated numerous defects. On

this basis 36 tubes out of 1285 were plugged. The entire problem was evaluated by an

outside panel of experts. The panel recommended the prompt replacement of the present aluminum heat exchanger by one made of stainless steel. The specifications of a new stainless

steel heat exchanger are almost completed and steps to obtain it will be taken shortly. It

is expected that the new exchanger will be ready for installation in about 1-1/2 years.

Total operating time lost was about 50 days.

B, SERVICE PROGRAMS

Service and irradiation programs have more than doubled over the last year. In all

more than 3000 irradiations involving over 20,000 samples were irradiated. These again

involved a wide range of people-oriented projects as well as research and application

programs. Of significance among the new programs is the preparation of Fluorine-18 for

scanning for bone cancer. Included among participating organizations are the major

governmental medical and health centers and major university medical centers in the area.

More specific summaries of the service and irradiation programs are outlined in succeeding

sections.

69
Fluorine-18 Radiopharmaceutical for Bone Lesion Localization

Major George Dunson and Ira Godwin

Northern Virginia Pathology Laboratories, Fairfax, Va.

John Harbert

Georgetown University Hospital, Washington, D.C.

and

Edward Embree

Fluorine-18 (F-18) has been known for several years as the agent of choice for bone

lesion imaging. The radioisotope administered orally or parenterally accumulates in bone in

direct proportion to the bone flow and metabolic activity. F-18 scintographs demonstrate

lesions far earlier than x-ray radiographs which require a 30% change in bone density in

order to produce lesion images. F-18 gives a sufficiently low radiation dose to patients to

permit its use in skeletal surveys and benign lesion imaging. The radiation dose of

strontium-85, the readily available bone imaging agent, is so high that its use is restricted

to patients with diagnosed primary carcinoma.

Fluorine-18 radiopharmaceutical was successfully prepared and used at Walter Reed

General Hospital for about two years. However, due to the small amounts being produced and

legal restrictions it could not be made available to the civilian medical community. F-18

could not be made commercially available to the Washington/Baltimore area because it has a

two hour physical half life.

Due to the great need for F-18 for patient use and the potential of the National Bureau

of Standards Reactor Radiation Division to make F-18 in large amounts several medical

institutions joined in a group project to make F-18 radiopharmaceutical at the National

Bureau of Standards. A goal was set of having 70 millicuries (mCi) F-18 in dispensing vials

and quality control and assay testing completed by 7 a.m. on the day of use.

Legal and administrative problems included absolution of the U.S. government from patient

responsibility, compliance with Atomic Energy Commission (AEC) radioactive materials licenses,

assuring the Food and Drug Administration (FDA) of drug safety and efficacy and adequate

records keeping, location of facilities and equipment for accomplishing the separation and

testing of a two hour half life material, and the availability of a radiopharmacist to

accomplish the project. The National Bureau of Standards Reactor Radiation Division

provided laboratory facilities and equipment, materials and supplies, and health physics and

70
reactor operations assistance and expertise. The Walter Reed General Hospital permitted its

radiopharmacist to direct the project in an off-duty individual responsibility status. The

FDA accepted the Investigational New Drug Application (IND) of the radiopharmacist, which

assured drug safety, high standards of drug processing and testing and adequate records

keeping. Relief of the government from patient liability was assured in three ways: the

off-duty status of the radiopharmacist; physicians at the individual institutions using F-18

as investigators under the IND sponsorship of the radiopharmacist; and participating medical

institutions executing statements of disclaimer of governmental responsibility. AEC license

compliance was achieved by transfers of F-18 radioisotope from the NBS AEC license to AEC

licenses of the participating hospitals.

Physical problems in the production of F-18 were solved according to the method

described in the companion article "Fluorine-18 production in the NBS Reactor".

Problems involved in the radiopharmaceutical processing of high activities of F-18

include the protection of the worker from ionizing radiation, elimination of large amounts of

tritium formed during the production reactions , preparing the drug for the desired route of

administration, and testing for radiation activity, radioisotopic purity, chemical purity

and drug stability.

The oral route of administration was chosen because it eliminated a requirement for

pyrogen and sterility testing. Pyrogen testing of a two hour half life material would have

necessitated maintaining a rabbit colony on site and a minimum of three hours delay in

distribution of the radiopharmaceutical. Studies previously published by the radiopharmacist

established the fact that for fasting patients oral and intravenous administration are

equally effective. Pyrogen free chemicals and sterile techniques were used in the

radiopharmaceutical processing of an isotonic product as a precaution in case the drug might

be mistakenly given intravenously on some occasion.

Readily achievable standards of pharmaceutical components were established: NaHCC>3 up

to 2% W/V; NaOH up to 3% W/V as an alternative to NaHC0 3

; Na2

SC>4 up to 3%; total sodium less

than 24 mg per mCi F-18 at completion of processing; tritium activity less than 20% of F-18

activity at completion of processing. All criteria were easily met and the tritium (H-3)

activity was less than 1% of F-18 activity using the method described in this article.

71
Controls used in the processing and packing of the drug include:

1. sterility and pyrogen tested stock reagents

2. pH test for alkaline chemical stability

3. flame test for lithium

4. Determination of F-18 activity by ionization chamber or liquid scintillation assay, or

both.

5. Determination of H-3 by liquid scintillation as an after packing control, prior to

receipt by investigators.

6. Calculation of inert components on a W/V%

7. Retention or recall of the product if it does not meet the standards given above.

8. Gamma spectrum analysis for nuclide purity of an irradiated control sample of each batch

of targets prior to receipt by investigators.

Worker protection from external and internal radiation hazard was accomplished by

working in a radioactive fume hood, using long handled tools behind lead brick barriers and

uitlizing mirrors for vision. After developing a semiautomated technique and practice at

working with mirror images a worker could accomplish the radiopharmaceutical processing three

times weekly without approaching occupational radiation exposure limits.

The method of separation, purification and assay are as follows:

The basic equipment consists of a distillation flask with receiver, a survey meter and

electric mantle as illustrated in Figure 1. A dry 300 ml distilling flask (A) was fitted

with a dry funnel and placed over an electric heating mantle (B) with the probe (C) of a

survey meter placed underneath. A porcelain dish (D) was placed under the condensor of the

distilling flask which was separated by a lead partition (E) . The whole set up was placed

inside a fume hood with proper lead shielding.

The tubes were broken into 1-2 inch bits inside a flexible plastic tubing and the glass

pieces with the powder were dropped into the flask. Forty ml of 50% H2SO4 was slowly added

through the funnel. Effervescence was allowed to continue nearly to completion, and the

flask was tightly stoppered. The heating mantle was turned on and the condensate was

collected in the porcelain evaporating dish containing 10 ml of 1.5% sodium bicarbonate of

parenteral quality. When the survey meter indicated a drop of about 95% of the radiation

level, the flask was moved aside from the heat and the condensor was put over a beaker

72
/s<«£5

Fig. 1. 73
containing sodium bicarbonate solution to trap radioactive contamination. The porcelain

dish was then placed on the heater and the solution was tested for the alkalinity necessary

to form heat stable ionic sodium fluoride. The condensate was flame tested for the carmine

color of lithium. The dish was heated until the solution was boiled to near dryness.

Twenty-five ml of water for injection was then added, and the solution was passed through a

membrane filter into a vaccine vial. Assay was accomplished by ionization chamber for F-18

activity, using 1/2 SH-85 as a standard, and by liquid scintillation for tritium. An initial

qualitative evaluation of H-3 can be done in the presence of F-18 when a narrow window is

used. Later a quantitative assay of H-3 can be performed.

Chemical assay was accomplished by calculation from volumes of solutions used. Biological assays were done during preliminary phases of the project.

The result of the project is that 70 mCi F-18 radiopharmaceutical can be made ready for

distribution to participating medical institutions by 7 a.m.

Fluorine-18 produced and processed at the National Bureau of Standards Reactor Radiation

Division has been successfully used in patients at the Fairfax Hospital, Fairfax, Virginia.

Georgetown University Hospital, Washington, D.C., the Johns Hopkins Hospital, Baltimore, Md.,

National Institutes of Health, Bethesda, Md. , National Naval Medical Center, Bethesda, Md.

Northern Virginia Pathology Laboratories, Fairfax, Va. , Veterans Administration Hospital,

Washington, D.C., and Washington Hospital Center, Washington, D.C.

74
Fluorine-18 Production in the NBS Reactor

laj or "George Duhson

Walter Reed General Hospital, Washington, D.C.

William Crofford

Department of Army Civilians, Fort Belvoir, Va.

and

John Ring

Fluorine-18 (F-18) is a 110 minute half life positron emitter that has been used

extensively, when available, for radios cintographic visualization of bone lesions.

F-18 has been produced in nuclear reactor and cyclotron facilities by a variety of

nuclear reactions. However, due to its short physical half life, its use has been

geographically restricted to institutions to which the radioisotope in pharmaceutical form

can be quickly delivered to the using nuclear medicine clinic. There are no medical use

cyclotrons or reactors in the Washington D.C. area so F-18 was undertaken in U.S. Army

nuclear reactors

.

F-18 was successfully produced in the Walter Reed Army Institute of Research (WRAIR)

nuclear reactor and the Diamond Ordnance Radiation Facility (DORF) nuclear reactor. The

WRAIR reactor was closed in February 1970. Due to the medium level thermal neutron flux

and operation hours of the DORF reactor a maximum of six millicuries (mCi) of F-18 per day

could be made available for patients. The F-18 could be available for pharmaceutical

processing no earlier than 11:30 a.m. The expense per production run of F-18 in the

medium power reactor was high because the reactor could not be used for other purposes for

up to three hours and the non-reuseable target material and target cost about $45.00 for

one irradiation with a maximum 6 mCi yield.

A project was undertaken at the National Bureau of Standards to produce F-18 in amounts

exceeding fifty millicuries. Additional goals were that the production did not interfere

with or prevent simultaneous reactor projects and the production could be completed by 6 a.m.

on the morning of use.

The only reaction available for nuclear reactor production of F-18 is a two step

reaction in which a thermal neutron splits a lithium-6 (Li-6) atom to give off a tritium

atom which enters an oxygen nucleus and forms F-18 upon the ejection of a neutron. These

reactions using enriched stable isotopic Li-6 as the carbonate are written as:

75
1. 6Li|n,ct| 3H 2. 16o| 3H,n| 18F

The cross section of the first reaction is 1000 barns and the cross section of the second

reaction is one-half of a barn. The physical difficulties in the production of F-18 are

primarily associated with the phenomena of heat generation when alpha particles are formed

and contained during the first step of the reaction. Secondary problems are associated with

using a target container and holder that neither becomes radioactive nor disintegrates in a

high thermal neutron flux. Problems dependent on the characteristics of the nuclear reactor

are the length and design of the target container and holder and method of placing them in

and removing them from the desired flux region.

The method developed for the production of F-18 was encapsulating the Li-6 carbonate

powder in thin quartz tubing, placing one to four of these tubes in a plastic holder, and

lowering and raising the holder with nylon cord in the water filled radiation facility into

the maximum flux area of the reactor. Characteristics of the quartz tubing are 3 mm inside

diameter and 3-1/2 inch length. The plastic holder has spacer holes to maintain tube

separation, holes for water circulation, lead sinker, and quartz wool for cushioning.

The results of the project far exceeded expectations. Each tube produces 34 mCi of F-18

at the end of two hours irradiation. A total of 136 mCi F-18 can be produced at any time

upon two hours notice without disrupting reactor operations or interferring with other

experiments or experimenters. The non-reuseable target and target material cost about $4.00

for one irradiation and a 34 mCi yield or about $13.00 for a 136 mCi F-18 yield.

The current status of the Army Fluorine-18 production project is that twice weekly F-18

is produced for a joint radiopharmacy operation of the Walter Reed General Hospital, National

Institutes of Health and National Naval Medical Center. F-18 is used by these institutions

for their patients and patients from other governmental hospitals.

The F-18 is extracted as sodium fluoride solution using a special separation process

on equipment installed at the NBSR facility. The F-18 solution is provided then in a form

suitable for oral administration.

76
Studies of the Effects of Parenteral Copper Chelates on Bone Healing

G. C. Battistone

U. S. Army Institute of Dental Research, Walter Reed Army Hospital, Washington, D.C.

During the past year experiments have continued on the effect of injected copper chelates

on bone healing in experimentally injured guinea pig bone. Neutron activation analysis was

used to analyze for the trace metals. Doses of copper salts as low as 50 pg Cu/day given to

experimental animals in previous experiments have demonstrated a high toxicity. In chelate

form the copper is better tolerated but remains toxic. The daily intraperitoneal injection

of 250 pg Cu/day as copper nitrilotriacetic acid has resulted in a noticeable acceleration of

bone healing in the guinea pigs. However, copper accumulation was noted particularly in the

liver and although animal deaths were not recorded the experimental animals did not show

normal weight gains. Other copper chelates administered at doses containing 100 pg Cu/day

did not produce toxic effects in the experimental animals but bone healing acceleration was

either minimal or absent. Since it now appears that injected copper chelates can accelerate

bone healing, and that copper toxicity can be diminished by administration in the chelate

form, studies are being directed toward the possibility of finding the appropriate copper

dose level and chelate which will produce optimal healing acceleration without toxic effects.

77
Activation Analysis Program of the Food and Drug Administration at the NBSR

J. T. Tanner, M. H. Friedman, M. Jaffee, L. A. Ford, and D. N. Lincoln

Food and Drug Administration, Washington, D.C.

1. Determination of Mercury in Common Foods and Total Diets

Data accumulated by the Food and Drug Administration and other government agencies have

demonstrated that fish is one commodity which introduces mercury into the diet. Fish,

however, only represents a small portion of the normal diet of the American public. It is

necessary therefore, to determine if there are other foods besides fish that contribute

significant amounts of mercury to the diet. Food samples of flour, sugar, non-fat dry milk,

potatoes, hamburger, chicken breast, shrimp, lever, eggs, and whole milk were analyzed for

mercury by neutron activation analysis. A modification of the Jervis procedure which involves

separation of the mercury by anion exchanger chromatography and sulfide precipitation was

used. The results of this study show that the common foods are well below 50 ppb Hg as used

by the World Health Organization. In all foods except shrimp the mercury was found to be

below 10 ppb.

2. Mercury Distribution in the Central Nervous System of Beagles

Mercury was determined by non-destructive neutron activation analysis in the central

nervous system of Beagle dogs which had been fed a diet of MeHgCl. The data were collected

by a low energy photon detector connected to a 1024 channel pulse height analyzer and then

reduced by a computer program. Results of the study point out that a) mercury in the dog's

brain is not distributed uniformly, b) from the scant data available we infer that the

mercury in the occipital cortex does not decline as was the case with the other structures,

and c) it appears that neutron activation analysis has the capability to determine mercury

levels even in the smallest discernible samples dissected from the central nervous system of

the dog.

3. Determination of Bromine in Pigs

This is a continuing program in support of FDA research of biological effects of

brominated vegetable oil. Tissues from pigs dosed with brominated vegetable oil containing

materials are being analyzed by non-destructive NAA.

4. Drug Analysis and Radioisotope Tracer Production

In addition to these projects several other problems were investigated. Thse include

a) the determination of Na, I, CI, Br in Ampicillian tablets from foreign manufacturers,

78
b) the determination of Hg in the hair and blood of a victim of mercury poisoning, c) the

irradiation of nuts to use as a tracer to simulate mycrotoxin and d) the determination of Al

in some drugs for regulatory purposes

.

5. Analysis for Mercury in Fish, Flour and Standard Reference Orchard Leaves by

Electrodeposition Radiochemistry

The use of electrolysis for the radiochemical separation of mercury-203 from other

interfering radionuclides in neutron activated food samples yields mercury of high purity

deposited on gold. However, modifications of published electrodeposition procedures were

necessary before acceptable results could be obtained by this method.

Some of these modifications included shielding the thermometer against thermal shock,

insulation of the reflux apparatus for uniform heating, and the use of hydrazine sulfate to

remove chlorine interference.

Although the high variability of yield of the mercury carrier indicates the need for

further modifications, the Hg-203 results were acceptable for a satisfactory comparison with

data obtained by different methods. The data acquired from the test samples by electrodeposition of mercury were in good agreement with the data obtained by other investigators

who used sulfide precipitation and gas chromatographic techniques.

Scandium Distribution in a Terrestrial Rock

John Barker and Hiroshi Nagasawa

Chemistry Department, University of Maryland

The bulk chemical composition of an igneous rock hides much of the history of formation

of the individual crystalline minerals in that rock. Silicate rocks, formed by cooling of

melts, have similar minerals on Earth, the moon and in meteorites. A thorough study of any

one of them should help in the understanding of all of them. Each and every element can provide unique information about the chemical evolution of the rock. Past results on the

geochemistry of scandium have failed to notice the high preference of Sc for Mg and Fe

containing minerals, relative to the residual liquid which is present in the rocks as a

glassy matrix. This preference suggests that Sc behaves like some rare earth elements. The

79
following results were obtained by instrumental neutron activation analysis, INAA, for

minerals from a dacite rock from a volcano in Japan:

Mineral Mineral Sc Distribution Ratio

Phase Chemical Formula (ug/g) (Mineral / Matrix)

Hypersthene (Mg,Fe)Si03 39.0 15.6

Hornblende NaCa2 (Mg,Fe,Al) 5 (Si,Al) 8 22 (OH) 2 187.2 74.9

Matrix glass 2.50 1.00

Distribution of Elements in Meteoritic Minerals

John Barker, David Nava, Philip Cressy and Patricia Buhl

Chemistry Department, University of Maryland

Minerals separated from a powdered sample of Bruderheim meteorite were analyzed for

iron, chromium, and cobalt by instrumental neutron activation analysis, INAA. The National

Bureau of Standards reactor was used, along with counting facilities at the University of

Maryland. Preliminary numbers are given in the table below, along with a comparison to the

literature which indicates that most of these elements have been accounted for with the phases

that were analyzed. Additional work on this and other elements in more purified phases

should yield information on the origin and evolution of meteorites. Work is in progress on

the separation of minerals from the Allende meteorite, which is believed to be representative

of the material from which the solar system originally condensed.

Fe Cr Co (microgram element per gram of phase)

113,300 1,350 13.7

175,000 1,330 16.4

783,000 - 5,610

587,000 26,400 33.1

Other 1.92%

Totals (INAA for above phases) 222,000 3,100 430

Totals (Bulk from literature) 223,000 3,600 500

80

Phase Formula Modal

Analysis

Pyroxene (Mg,Fe)Si03 42.26%

Olivine (Mg,Fe) 2Si04 40.67%

Metal Fe,Ni 7.60%

Troilite FeS 6.71%

+ Chromite Fe0Cr9

0-, 0.85%
Trace Elements in the Environment

G. E. Gordon, W. H. Zoller, and W. B. Walters

University of Maryland, College Park, Maryland

Our major use of the NBS reactor to date has been the irradiation of atmospheric

particulate material collected on various filter material. Using instrumental neutron

activation analysis we routinely determine concentrations of approximately 20 elements by

the use of Ge(Li) y-ray detectors. An extensive study of the particulate material in the

atmosphere of Boston has nearly been completed with the analysis of approximately 200 samples.

High concentrations of vanadium (up to several yg/m ) from the combustion of residual fuel

have been observed. In addition, studies of the chemical composition with respect to size

of the particles has indicated that some trace elements such as V, Sb, Zn and Br are

predominantly attached to small particles where as others, such as Fe , Na and CI, are on

large particles. These studies group many of the elements into categories which may be

indicative of the source of the various particulates.

Initial work on source materials such as residual fuels has shown that very high

concentration of many elements are present and are presumably released into the atmosphere

upon combustion. An example of a trace metal introduced into the atmosphere in high

concentration is V, which has concentrations up to 800 ppm in residual fuel oil samples. We

are presently extending these fuel analysis projects to distilled fuels such as kerosene,

fuel oil and various lubricating oils.

We are presently performing the analysis of a group of atmospheric particulate samples

from Antarctica. These samples are difficult to analyze due to the very low concentrations

involved. We are detecting only small concentrations of various elements above the filtermaterial blanks. This project will be continued over the next three years in order to measure

the concentration of the trace elements present in this very clean "background" area.

Several groups of samples from New Zealand have been analyzed to determine the

contribution from the largest cities to the circulation of pollutants in the Southern

Hemisphere. A set of samples from four sites will eventually be analyzed for several trace

elements over a period of five years. The results of these analyses should indicate any

changes in the chemical composition of the particulate material since implementation of

anti-pollution laws in Auckland and Christchurch, New Zealand in the past few years.

81
A project on the analysis of water samples for trace elements has been initiated.

Samples can be analyzed directly for several elements that are present in high concentrations.

Various pre-irradiation concentration steps are being tested in an attempt to increase the

analytical capabilities of neutron activation analysis as applied to water samples. Some

post-irradiation chemistry such as solvent extraction or sodium removal are also being

tested in order to improve our ability to analyze for certain elements such as V and As.

Samples have been collected from the Pautuxant and Potomac Rivers for the program. We will

be studying the distribution of trace metals (transition metals) between the dissolved and

particulate phase in a natural water system.

Work on new and better standards using lactose and cellulose pellets doped with various

trace elements has produced encouraging results to date. Reproductability of some elements

appears to be well within 1 to 2% on several standard pellets. This work is done in

cooperation with Dr. Harry Rook of the Activation Analysis Section of NBS.

A number of isotopes have been produced for radioactive decay studies and for tracer

studies of chemical reactions. Thirty-hour Te-131m has been produced by the ^-^^Te(n,Y) 13 -'-Te

reaction in order to study the decay of Te-131m and the levels of 1-131. Preliminary studies

have also been made on 25-min Se-83, 42-sec and 4.36 min Rh-304 isomers, and 4.44 hr Ru-105.

Radioactive Se and Te nuclides have been prepared for use as tracers in studying separations

of Se and Te in environmental pollutants. A number of radioactive isotopes have also been

prepared for use as standards in calculating the energy response and efficiency of Ge(Li)

y-ray detectors.

82
The Use of Neutron Activation Analysis in Scientific Crime Detection

Forensic Staff, M. J. Pro, Chief

U. S. Treasury Department, Washington, D. C.

The value of NAA for examining physical evidence such as paints and soils is well

documented. The findings obtained by NAA have been introduced as court evidence many times

and its use has been upheld by Appellate Courts when tested by appeal.

The U. S. Treasury Department utilizes NAA extensively for the examination of a wide

variety of physical evidence and the activation of specimens at the NBS Reactor is almost a

daily event. In the past year 1850 samples from 300 criminal cases were processed by this

method. The types of samples are quite diverse ranging from cotton swabs bearing traces of

gunshot residue to heroin confiscated at a U. S. port of entry. While the NBS Reactor was

undergoing repair this summer, the Treasury Laboratory used the Western New York Research

Center Reactor in Buffalo, New York to examine 1500 gunshot residue samples in 190 criminal

cases. This type of examination is requested by police departments across the country who

have learned the value of NAA for detecting the presence of gunshot residue in cases involving

the use of firearms

.

The potential use of NAA for examining such unusual materials as coffee beans is being

explored by the Treasury Laboratory in connection with U. S. Customs Bureau investigations.

Beans from more than a dozen locations throughout the world are being examined to determine

if meaningful differences exist in their trace elemental compositions. These data when

correlated with other information may prove useful in establishing the country of origin of

the coffee beans which is relevant to the import duty imposed on this commodity.

Since October, 1970 the cases in which the NBSR facility was used by the Treasury

Laboratory are summarized below:

Type of Case Number of Cases

Crimes of Violence (Gunshot) 225

Production of Illicit Spirits 40

Destructive Devices 20

Drug Abuse 5

The Treasury Laboratory's present NAA capabilities are being expanded by the aquisition

of a new 60 cc Ge(Li) detector coupled to a Data General mini computer. It is anticipated

83
that once the system is operational a significant increase in the number of samples

processed by NAA will be possible.

Federal Bureau of Investigation Activation Analysis Program

J. Kilty, J. Riley, G. Mahoney

Federal Bureau of Investigation, Washington, D.C.

The FBI Laboratory is conducting trace elemental analysis of copper wire in order to

determine the homogeneity of the trace elements along the length of wire and to measure the

variations in concentrations of the trace elements in different wires of the same gauge. The

elements usually detected in copper wires are selenium, gold, silver and antimony. Due to

the high cost of copper, thefts are a common occurrence and neutron activation analysis

offers a method for the possible association of copper from the scene of a theft with copper

recovered from the suspect or a salvage yard.

Many other types of evidence are received for analysis in the FBI Laboratory. Metals

such as lead, steel and aluminum are analyzed on a routine basis for both the FBI's cases

and for local law enforcement agencies. Examples of samples which are run on a less routine

basis are biological samples which are analyzed for arsenic or other elements common in

poisons, plastic-type materials and paint.

Paraffin and cotton used to remove gunpowder residues from the hands of a person

suspected of having discharged a firearm are analyzed by NAA for the elements antimony and

barium, which are components of most primer mixtures. This work has been conducted for the

past four years and has formed the research upon which analyses are based today.

In April, 1970, investigators in a southern city were confronted with two slain

individuals who were either the victim of a double murder or a murder - suicide. Analyses

of the casts taken from the two slain individuals and the suspect's hand indicated that one

of the slain persons had discharged a firearm. After all the facts were considered, the

investigators ruled a murder - suicide had taken place and the suspect was released.

84
U. S. Postal Service Activation Analysis Program

Gordon Stangor, James Upton, and Michael Beckman

Crime Laboratory, U. S. Postal Service, Washington, D.C.

During the past year, the U. S. Postal Service Crime Laboratory continued using the NBS

nuclear reactor facility for forensic applications. Types of evidence items irradiated at

NBS and regularly analyzed by the neutron activation technique include glass, paint, hair,

metals, tape, paper, and safe insulation. Much of this evidence is derived from investigations

relating to post office burglaries and bomb mailings.

Presently, research is underway to make determinations as to the extent that

compositional trace elements vary in safe insulation produced by a single manufacturer. It

is hoped this will provide the basis for identification of a particular safe within a given

manufacturer's production.

In an important decision relating to the results of neutron activation analysis, the

Supreme Court on March 29, 1971, denied a petition for certiorari of an Appeals Court

affirmation pf the conviction of the mailer of a bomb parcel which had exploded and killed

the addressee. Review of the case was petitioned on grounds that the process of neutron

activation employed in making comparisons of certain bomb components (paper, metal, and

plasti/c tape) was relatively new and had little legal precedent. The Appeals Court in

upholding the admission of expert testimony concerning this method of analysis stated

" neutron activation analysis has gained 'general acceptance in the particular field in

which it belongs.'" and that it " meets the test of admissibility "

85
Development of Analytical Methods and Determination of Constituents

of Ge6logical Samples

J . J . Rowe

U. S. Geological Survey, Washington, D. C.

The Radioactivation and Radiochemistry projects of the U. S. Geological Survey has been

using the NBS reactor facilities for irradiation of rocks and minerals for the development

of analytical methods and to provide analytical services to geologists.

Some of the services and studies made during the year are:

1. Analysis for Gold in Rock Samples - J. J. Rowe

Rock samples have been analyzed for gold in studies of background levels and magnetic

fractionation. One gram samples were irradiated for one hour in RT-3, along with standards.

Irradiated samples are cooled for ten days to permit decay of short lived activity. Samples

are then processed, with carrier gold, using fire assay to obtain a gold bead which is

counted on Nal(Tl) detectors. The 0.413 meV peak of Au-B8 is used for the determination.

This method permits the determination of gold at concentrations as low as 0.1 ppb. A

publication summarizing the data on more than 700 samples is in press (Gottfried, Rowe and

Tilling, "Distribution of gold in igneous rocks", U.S.G.S. Prof. Paper 727).

2. Gold as a Tracer in Thermal Waters - Rowe and Schwarz

Techniques have been studied for the concentration and collection of gold in thermal

waters using Au-295 as a tracer to monitor the efficiency of the ion exchange collection.

Resins are irradiated for 10 minutes, cooled one day, and processed by fire assay to destroy

the resin and collect AuA95 and Au-B8 in a gold bead. The Au-195 is used to determine yield

from original sample, through ion exchanger concentration, irradiation and radiochemistry.

Concentrations of gold in thermal waters vary from 0.005 ppb to as high as 0.1 ppb. The

technique is being developed for use in field collections to avoid problems of gold plating

out on walls of containers. A similar procedure is being developed for collection and

concentration of mercury.

3. Trace Metals in Galena, Sphalerite, Pyrrhotite and Pyrite - Simon and Rowe

Samples of galena, sphalerite, pyrrhotite and pyrite were analyzed for Cu,Zn,Sb,Au,Ag

Mn,Cd, and Se using instrumental, coincidence and radiochemical methods. The results have

been published in Economic Geology v. 66, p. 602 (1971) "Fractionation of minor elements

86
between galena, sphalerite, Darwin Lead-Silver-Zinc Mine, Inyo County, California and its

significance in geothermometry" by Hall, Rowe and Simon.

4. Analysis for La,Sc,Cr,Th, and Au - J. J. Rowe

Various samples submitted by geologists have been analyzed for La,Sc,Cr ,Th, and gold by

radiochemical and instrumental methods.

5. Determination of Platinum and Palladium in Geological Materials - J. J. Rowe

Samples from various localities were analyzed for platinum and palladium using fire

assay preconcentration and radiochemistry. Ten to twenty gram samples are processed by fire

assay to concentrate the platinum and palladium into a 3 mg silver bead. The silver beads

are irradiated for two hours, and then platinum and palladium are radiochemically separated

for beta counting following the procedure by Rowe and Simon, "Determination of platinum and

palladium in geological materials by neutron activation analysis after fire assay preconcentration" , Talanta, v. 18, p. 121-125 (1971). Concentrations of platinum as low as 3 ppb and

palladium as low as 1.5 ppb were found in samples from the continental shelf. A study of

platinum and palladium in various igneous rock provinces is being made.

6. Determination of Tantalam, Antimony, and Hafnium in Lunar Samples - Greenland

Lunar samples have been irradiated for the determination of tantalum, antimony and

hafnium.

7. Background Levels of Arsenic in Rocks and Soils - J. J. Rowe

A radiochemical method is being tested for the determination of arsenic, using As-77 for

the yield determination. A comprehensive study is being made of background arsenic levels in

rocks and soils as part of the study of environmental pollution.

87
Study of Radiation Effects on the Transmission Characteristics

of Sapphire and Quartz Windows

R. E. Patrick

(U.S. Arms Control and Disarmament Agency, Washington, D.C.)

0. E. Frizzell and J. H. Ring

The purpose of this program was to measure the degradation in the light transmission

characteristics of sapphire and quartz windows that had been exposed to a high neutron/

gamma field. The general trends observed during the irradiating period were given primary

consideration and little effort was made to insure high precision in the measurements.

The general philosophy was based on the goal of the program which was to provide engineering

support to the efforts to develop a unique identification system for arms control and

international material safeguards application. The time frame under which this program

operated prevented the experimenters from developing the sophistication and precision which

one would normally strive to achieve.

The experimental procedure involved a cycle of events which include a specified

irradiation period, cooling and measurement of the light transmission characteristics.

The NBSR rabbit system was utilized in the irradiating period. This cycle was repeated

until the desired total flux of 5.0 x 10^- 9n/cm was attained. The characteristics of the

flux field were approximately a thermal neutron flux of 5 x lO^n/cm -sec and high energy

13 2 (E>/Mev) gamma flux of about 6 x 10 y/ cm -sec

The procedure used in measuring the light transmission characteristics involved the

use of a beam splitter window and a red lens window. The red lens window was used to

determine the degradation of transmitting red light through each window and the beam

splitter was used as a standard to compare to. Figure 1 illustrates the experimental

set-up.

In configuration B light passes through the beam splitter where part of it is absorbed.

The remaining light then travels through the red lens and is measured by the light meter.

In configuration A the light passes through either the sapphire or quartz window then

through the red lens and is measured by the light meter. Readings without the red lens

mounted in the configuration were also taken. There was also 3 different settings of the

intensity of the light source.

88
The results of configuration A, with and without the red lens, could then be compared

to the results of configuration B. The value of the measurement in configuration B

should always remain constant thereby offering a benchmark to calibrate the experiment.

The following table summarizes the results of this experiment.

PERCENT OF SOURCE LIGHT TRANSMITTED

Irradiation Light Beam

Level ( n/cm2

) Intensity Saph Saph/Red Quartz Quartz/Red Splitter BS/Red

High 100 23.4 100 22.2 33.1 7.8

Med 100 19.0 100 23.1 32.4 8.8 Low 100 19.2 100 20.7 30.4 3.6

7.2xl0

17 High 90.1 23.4 100 22.2 33.1 7.8 Med 79.4 19.0 100 23.1 32.4 8.0 Low 73.3 19.2 100 20.7 30.4 3.4

1.44xl0

17 High 83.6 23.9 100 25.4 33.4 7.6 Med 83.8 22.6 100 25.4 32.4 7.3 LOW 84.2 23.5 100 26.1 30.4 7.3

5.0xl018 High 82.9 23.0 100 25.8 33.5 9.8

Med 81.0 22.2 100 25.6 31.4 7.1 Low 81.9 21.5 100 26.1 31.1 7.3

19 3.5x10 High 62.6 18.1 98.5 25.2 33.4 7.4 Med 61.5 17.8 98.4 24.8 31.6 7.1 Low 61.7 18.5 99.8 26.1 29.8 7.2

5. 0x10

19 High 61.0 18.2 100 26.1 34.9 7.8 Med 58.3 17.1 100 26.2 31.9 6.9 Low 56.5 17.7 99.8 25.8 29.2 6.9

In addition to the above measuremsnts a more precise light transmission curve was

made at the beginning, end and one intermediate point in the irradiation cycle. The

following curves, Figs. 2 and 3, illustrate the results of these measurements.

89
Based on the results of this experiment the following conclusions were reached.

1. Sapphire Window

a. There was a general degradation (30-40%) of the light transmission

characteristics for "white light.

b. The radiation effects on the transmission of light in the red region were

(^5%) when compared to the beam splitter.

c. There was considerable degradation (70-80%) of light transmission characteristics

in the blue region.

2

Quartz Window

a. There was only limited degradation for "white" light.

b. There was no predominant frequency (red or blue) in which this limited

degradation occurred.

The results of this program were submitted to Sperry, an ACDA contractor, and will

now be incorporated into the research and development program.

f J Light Source f A

Sapphire/Quartz J" Beam

Window Splitter

Red Lens Red Lens

r

Light Meter J

Fig. 1. Experimental Configuration

90
1.0 —

.75

•H

.25

Light Source only

Lens Only - No irradiation

3.5 x 10

19 nvt

5.0 x 10 19 nvt

± -L

350 900 Light Wavelength

Fig. 2. Sapphire Window Light Transmission Characteristics

1.00

.75

•Ha«

•ua

•M•&

•H

.50

.25

Light Source only

All Irradiations

350 900

Light Wavelength

Fig. 3. Quartz Window Light Transmission Characteristics

91
Feasibility Investigations of a Fuel Bundle Motion Monitor

J. P. Boright, R. E. Patrick

(U.S. Arms Control and Disarmament Agency, Washington, D.C.)

and

0. E. Frizzel

A joint Canadian-American group is developing un-attended instrumentation for IAEA

safeguards (as required by the nuclear Non-Proliferation Treaty) . One component under

development is a pair of collimated ion chambers for monitoring irradiated reactor fuel.

The difference signal from the two chambers can yield directional information on fuel

bundle movement.

Some aspects of the proposed bundle monitor have been investigated using the spent

fuel in the bay at the NBS reactor. The uniformity of the chambers, and their performance

in high fields was measured. Attenuation and spatial smearing of the observed signals was

investigated as a function of distance from the fuel , and of material between the fuel and

the monitor. Also, effects of background signals in various geometrical configurations

were investigated. With the results, qualitative estimates can be made of the signals

expected in given monitoring siturations. These monitors are now being tested at a

nuclear reactor and are being prepared for use at a reprocessing plant.

92
Investigation into Neutron Damage of PbS Films

R. M. Cullpepper

(Naval Ordnance Laboratory, White Oak, Maryland)

NOL has undertaken an investigation into the neutron induced damage in PbS semiconducting films. The electrical properties of both n and p type films (the mobility,

resistivity and the number of free carriers) have been measured from 4.5°K to 800°K at

NOL before and after each of as many as five irradiations. The samples were irradiated in

100 minute steps in the RT-2 facility of the NBS reactor operating at 2Mw. The data

obtained from these measurements was then used to determine free carrier removal rates,

scattering mechanisms , and radiation induced energy lying near the band edges . The samples

used in this experiment were grown in triplets on an NaCl substrate at NOL. Two of each

set of three were then transfered to a plastic backing and the NaCl substrate disolved off,

while the third remained on the NaCl. The effect of this transfer on the electrical

properties was not measured, but the variation in electrical properties across the triplet

samples after transfer was no greater than the variation in triplets still on an NaCl

substrate. All three samples of each set were exposed to similar environments except one

of the plastic backed films was subjected to irradiation. When the irradiated sample

was measured after each irradiation, each of the other two was also measured. This was

done because no data existed describing aging effects of such films , either on the NaCl

substrate or on the plastic backing, it was discovered that aging lowers the carrier

concentration of both types of unirradiated films, but not enough to be significant in

the experiment.

The results indicate that the carrier concentration of both n and p type samples is

lowered by irradiation. The carrier removal rate is approximately 4 free carriers/fast

2 neutron per cm . There appears to be no irradiation induced energy levels within .02ev

of the band edges. The mobility data indicates that the irradiation introduces no new

scattering mechanisms. The use of the Mansfield-Dingle mobility equation to compute the

number of defects introduced into the irradiated films leads to results that vary widely

from sample to sample, and from the result predicted on the basis of various cascade

displacement models, it is felt that the cause for such disagreement might be that the

irradiated material is a new form of PbS , containing both interstitials and vacancies of

Pb and S, whereas the as grown PbS has only vacancies of both elements. It is further

hypothesized that these interstitials form some sort of amphoteric trap for the free

93
carriers. The nature of this trap is not known; it could be a system of donor and acceptor

levels near the center of the band as has been shown to be the case in silicon, or a single

level which may capture either a hole or electron, as does the level introduced by gold

in germanium, or some even more complicated scheme not apparent from the data at hand.

Neutron Irradiation of InSb

John Stannard

(Naval Research Laboratory, Washington, D.C.)

The Naval Research Laboratory is studying the effects of band tailing in heavily

doped indium-antimonide . Of particular interest is material doped with very nearly equal

concentrations of donor and acceptor impurities. Transmutation of In-115 into the donor

Sn-116 allows such closely compensated material to be produced when initially P-type

material is irradiated with thermal neutrons . To date experiments have been performed to

show the production rate of donors in the RT-4 facility. In addition a series of samples

has been irradiated so as to become closely compensated. These samples are now being analyzed

Neutron Activation Analysis of Silicon for MOS Devices

J. Repace and H. L. Hughes

(U.S. Naval Research Laboratory, Washington, D.C.)

As part of a continuing program in the Reliability Physics of MOS devices, experiments

in our laboratory have established that the presence of sodium impurities in silicon

devices substrates plays a crucial role in enhancing the failure of these devices upon

exposure to ionizing radiation. We have therefore undertaken to measure the sodium

impurity levels in a variety of silicon substrates, using neutron activation analysis.

The presence of sodium is detected via the 1368.562 keV and 2753.92 keV gamma ray lines

23 24 of Na-^4 produced in the Na (n,y) Na reaction; the gamma rays are detected by an 80 cc

Ge(Li) detector with a 4096 channel pulse-height analyzer, and the data, on magnetic or paF

,c 3 . tape, are processed by computer. Sodium levels of the order of 10 x -) atoms per cm in

13 2 unprocessed device wafers and of the order of 10 atoms per cm in processed wafers have

been found. Further experiments to determine the sources and distribution of the sodium

impurity are planned.

94
Chemical Composition of Particulates Collected in the Marine Atmosphere

P. E. Wilkniss

(Naval Research Laboratory, Washington, D.C.)

Pollution of the marine atmosphere is steadily increasing, as indicated by increased

lead concentrations in polar ice samples and ocean surface waters, by the observance of

pesticides transported with wind-blown dust over the Atlantic and Indian Oceans and by a

general increase in ambient aerosol concentrations probably of man-made origin. Pollution

assessment in the marine atmosphere is very difficult for various reasons and the

analytical problems encountered require use of the most sensitive analytical techniques

known to date. We have investigated the use of neutron activation, to determine the elements

Na, S, CI, K, Ca, Mn, Br, Sr and I in particulate samples from the marine atmosphere.

Activation analysis of the aerosol samples was shown to be an excellent method for

determining the listed elements. The implication for pollution studies is that, by

determining elemental ratios such as F/Cl, Na/Cl, Na/K, Ca/S and Mn/Cl, one can determine

whether an aerosol is of natural origin (the ocean, or volcanic activity) or of man-made

origin.

Studies of Magnetic Properties in Rare Earth Alloys at Cryogenic Temperatures

R. Segnan and D. M. Sweger

(American University, Washington, D.C.)

A Mossbauer effect source of Dy-161has been prepared in a matrix of Gd203 for use in

magnetic rare earth alloys studies of cryogenic temperatures. A high velocity drive

(±25 cm/sec) has been assembled for use in measuring resonant absorption in Dy-161.

Magnetic rare earth alloys offer promise of possible use as materials suitable for high

energy density electromagnetic applications. Particularly promising are Dy-Gd and Dy-Y alloys,

since these tend to have quite attractive magnetic properties (for example, dysprosium has a

saturation magnetization of approximately 34 kilogauss at 4.2°K).

The alloy system Gd-Dy can be investigated by Mossbauer spectroscopy by using a

suitable radioisotope of either Gd or Dy. An analysis of the properties and availability of

possible radioactive sources led to the selection of a Dy-161 isotope. The Y~raY used in this

case comes from the decay of the 25.6 KeV excited state to the ground state in Dy-161. Tne

95
excited state of Dy-]61 can be populated by thermal neutron irradiation of Gd-160.

Gadolinium oxide, Gd203, enriched to 96% Gd-160 in the form of a fine powder is the

source material. The source is activated in the RT-4 pneumatic facility of the National

Bureau of Standards Reactor in a thermal neutron flux of 1.3 x 10^3 neutrons/cm^/sec . Such

a flux will yield a source strength of about 3 millicuries/hr/gram of enriched Gd203.

The splitting of the saturation hyperfine field in Dy-lfiL is 43.7 cm/sec and thus the

drive must be capable of peak velocities of about ±25 cm/sec. Velocities such as these are

at least an order of magnitude larger than are required for most other Mossbauer isotopes.

In addition, as for all drive systems, the velocity must be linear to within 1%. A modified

version of the NBS Mossbauer drive was used to achieve the high velocities required for the

Dy- 161 resonance.

In order to test the Mossbauer source, absorbtion spectra were taken with the low

velocity drive. Absorption vs. velocity curves were obtained for Gd2C>3 and Dy2^3 against a

Dy2°3 absorber. The full-width at half maximum of the Mossbauer absorption peaks obtained

were 1.8 cm/sec and 2 cm/sec respectively. As one can see the linewidths are comparable.

The relative resonant absorption is respectively 5% and 4%. All the measurements were taken

at room temperature. Presently, measurements are being performed on Dy-Gd alloys at room

temperature and liquid nitrogen temperature. Preliminary results on these alloys will be

available in the near future.

96
STAFF ROSTER

A, Division Organization Chart

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97
B. Non-RRD NBS Staff Located at Reactor

Division 310.08

D. A. Becker

B. S . Carpenter

T. Gills

M. L. Kehrer

D. Ishii

W. D. Kinard

P. D. LaFleur

G. J . Lutz

L. T. McClendon

J. Olin (Smithsonian Inst.)

H. L . Rook

R. W. Shideler

J. E . Suddueth

B. A. Thompson

H. P. Yule

Division 313.07

B. Mozer

Division 240.01

A. L. Ahalt

P. R. Cassidy

H. E. DeSpain

E. J. Embree

J. J. Shubiak

Division 242.01

R. A. Dallatore

J. A. Grundl

I. A. Schroder

C. Guest Workers and Collaborators

Division 221.03

B . Dove

H . Marshak

R. J. Soulen, Jr.

Division 221.05

R. D . Mountain

H . J . Raveche

Division 232.06

R. D. Deslattes

W. C. Sauder

Division 242.02

L. D. Miller

F. J. Schima

Division 311.03

J. D. Barnes

Division 311.05

B. Dickens

L. W. Schroeder

R. M. Waterstrat

Division 313.01

C. W. Reimann

Division 313.06

A. D. Mighell

Argonne National Laboratory

H. Flotow

D. C. Price

J. M. Rowe

Department of Army Civilians

W. Crofford

Federal Bureau of Investigation

J. W. Kilty

J. M. Little

G. P. Mahoney

J. P. Riley

Food and Drug Administration

M. Friedman*

M. W. Heitzman

M. Jaffee

D. N. Lincoln

R. E. Simpson

J. T. Tanner*

Harry Diamond Laboratory

C. A. Morrison

D. B. Wortman

Northern Virginia Pathology Lab., Inc.

C. B. Cook

Located full-time at NBS Reactor

V. A. Hospital

B. J. L. Sauerbrunn

98
Naval Ordnance Laboratory

H

Alperin*

R. M. Cullpepper

S. J. Pickart*

J. J. Rhyne*

R. H. Williams*

R. Youshaw

Naval Research Laboratory

G. A. Ferguson

H. L. Hughes

J. Karle

L. F. Paolella*

J. Repace

J. Stannard

P. E. Wilkniss

Pi catinny Arsenal

C. S. Choi*

K. W. Logan

R. Munroe*

H. J. Prask

R. S. Singh*

S. F . Trevino*

U. S. Arms Control Disarmament Agency

J. D. Boright

R. E. Patrick

U. S. Army Inst, of Dental Research

G. C. Battistone

U. S. Geological Survey

F. W . Brown

R. Finkelman

L. P. Greenland

J. J . Rowe

G. Sellers

F. 0. Simon

U. S . Treasury Department

P. C. Buscemi

c. M. Hoffman

F. A. Lundgren

M. J. Pro

N. B. Snow

W. D. Washington

Hanford Engineering Development Lab.

L. S. Kellogg

W. N. McElroy

American University

B. T. Chertok

R. A. Segnan

R. Simon

D. M. Sweger

Harvard University

J. L. Alberi*

R. Wilson

McGill University

G. Donnay

Temple University

M. Green

V. P. Warkulwiz*

U. S. Naval Academy

C. S. Schneider

University of Maryland

J. Barker

F. B . Birkner

P. Buhl

E. Gladney

G. E . Gordon

J. Graber

S. Harrison

A. Jones

R. Khanna

V. J. Minkiewicz

J. Ondov

J. Reednick

W. B. Walters

W. H. Zoller

Georgetown University Hospital

J. F. Stapleton

John Hopkins Hospital

S . Hosain

National Institutes of Health

G. S. Johnson

National Naval Medical Center

J. W. Duley

D. Manley

Walter Reed Army Medical Center

G . Dunson

99

FORM NBS-1MA (1-71)

1. PUBLICATION OR REPORT NO. NBS-TN-714

2. Gov't Accession No.

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Reactor Radiation Division: Annual Progress Report for the

Period Ending October 1, 1971

5. Publication Date March 1972

6. Performing Organization Code

7. AUTHOR(S) 8. Performing Organization

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. Project/Task/Work Unit No. NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

11. Contract/Grant No.

12. Sponsoring Organization Name and Address Reactor Radiation Division

National Bureau of Standards

Washington, D.C. 20234

13. Type of Report & Period Covered Interim

10/1/70 - 10/1/71

14. Sponsoring Agency Code

IS. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) The report is the annual progress report of the Reactor Radiation Division for

the period October I, 1970 to October 1, 1971. It summarizes the activities of the

large number of users outside the Division as well as the work in the Division.

''• KEY WORDS (Alphabetical order, separated by semicolons)

Crystal structure; diffraction, isotope, molecular structure; neutron; nuclear reactor;

radiation

] 8. AVAILABILITY STATEMENT

BUNLIMITED.

I | FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE

TO NTIS.

19. SECURITY CLASS

(THIS REPORT)

UNCLASSIFIED

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

21. NO. OF PAGES

108

22. Price

$1.00

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